OpenSSL Security Advisory [25th August 2026]
=========================================

QUIC Server May Trigger Double Free When Processing INITIAL Packet (CVE-2026-18798)
===================================================================================

Severity: Moderate

Issue summary: QUIC server may double free QRX (QUIC record layer RX) object
when channel creation fails for initial packet.

Impact summary: Double free leads to heap corruption, which typically results in 
termination of QUIC server process, leading to Denial of Service. There is so
far no evidence that this double free is exploitable for remote code execution,
thus it is considered highly improbable.

CWE: CWE-415: Double Free

Description: In order to validate initial packet, OpenSSL QUIC stack default
packet handler (port_default_packet_handler()) creates a so-called QRX object.
If the initial packet validates successfully with QRX object, the default packet
handler proceeds to channel (connection object) creation. The QRX object used
for packet validation is passed to port_bind_channel(), so it becomes part of
the newly created connection. If port_bind_channel() fails, then it also frees
the QRX object. Once port_bind_channel() returns, the port_default_packet_handler()
detects the failure and proceeds to the error branch, where the same QRX object is
freed for the second time.

The failure in port_bind_channel() function can be induced with a relatively
low effort by a malformed (non RFC 9000 compliant) INITIAL packet. If the packet
carries DCID (destination connection ID) which is shorter than 8 bytes, then
port_bind_channel() jumps to the error path after ossl_quic_lcidm_enrol_odcid()
detects that the DCID has invalid length.

FIPS impact: no
The FIPS module is not affected, as the QUIC implementation is outside of
the OpenSSL FIPS module boundary.

OpenSSL 4.0, 3.6, and 3.5 are vulnerable to this issue.

OpenSSL 3.4, 3.0, 1.1.1 and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8

This issue was reported on 27 July 2026 by Fuzz0x (ZKSC Institute of Security
Research), on 1 August 2026 by Emilio Galle and on 16 August 2026 by
Feng Xue (ThreatBoon).
The fix has been developed by Alexandr Nedvedicky.

Heap Buffer Overflow in CMS Key Unwrapping (CVE-2026-63072)
===========================================================

Severity: Moderate

Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based
on querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive
can write and cleanse more bytes than that query reports, causing an 8-byte
out-of-bounds heap write.

Impact summary: An attacker who supplies a crafted CMS message can trigger a
deterministic 8-byte out-of-bounds heap write when the victim decrypts it
with CMS_decrypt(), corrupting the heap and typically resulting in a Denial
of Service.

CWE: CWE-787: Out-of-bounds Write

Description: The key-wrap OID is potentially attacker-controlled on the wire.
CMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers.
An attacker can take a legitimate message and change a single OID byte to
select the padded variant while leaving the message otherwise valid. Since
the unwrap key is derived from the recipient's private operation (ECDH key
agreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot
pass, and the decryption fails with integrity failure.

The write is a fixed-size (8-byte), fixed-value (zero) heap overflow
immediately past the allocation, requires no special configuration, and is
reachable from the public CMS_decrypt() function. The consequence is
a heap corruption leading to a Denial of Service. The fix in the CMS code
sizes the unwrap output buffer for the worst case so a failed unwrap cannot
write past the allocation.

FIPS impact: no

As the CMS code lives outside the FIPS module boundary, no FIPS
modules are affected by this CVE.

OpenSSL 4.0, 3.6, 3.5, 3.4, 3.0, and 1.1.1 are vulnerable to this issue.

OpenSSL 1.0.2 is not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.

Premium support customers only:
OpenSSL 1.1.1 users should upgrade to OpenSSL 1.1.1zi

This issue was reported on 18 June 2026 by Bhabani Sankar Das and
independently by Filipe Casal (Trail of Bits) on 29 June 2026.
The fix has been developed by Daniel Kubec.

Invalid Pointer Dereference in CMP Server via Crafted protectionAlg (CVE-2026-63076)
====================================================================================

Severity: Moderate

Issue summary: OpenSSL CMP password based protection verification only
checks whether the protectionAlg parameter was not NULL and not its
ASN.1 type, before treating it as a PBMParameter. A crafted message can
contain a parameter of a different type, which is then dereferenced as an
invalid pointer.

Impact summary: A remote, unauthenticated attacker can crash an application
acting as a CMP server that accepts PBM-protected messages, or a CMP client
talking to a malicious or intercepted CMP server, resulting in a Denial of
Service.

CWE: CWE-476: NULL Pointer Dereference

Description: When verifying the password-based MAC protection of a CMP
message, OpenSSL library reads the protectionAlg algorithm parameter with
X509_ALGOR_get0(), which returns both the parameter type and its value
pointer. The value is then cast to an ASN1_STRING and treated as the
expected PBMParameter after only checking that pointer is not NULL. The
parameter type returned by X509_ALGOR_get0() was never consulted.

This happens during protection verification, before any MAC is computed, so
no knowledge of the PBM shared secret is required; the only precondition is
that PBM verification is reachable. On the server side this is reached from
OSSL_CMP_SRV_process_request() for any application that stands up a CMP
server accepting PBM-protected messages, and on the client side from CMP
response validation against a malicious or on-path (MITM) server. The
reliable consequence is a denial of service; there is no memory disclosure,
no controlled memory write, and no path to code execution. CMP is a
specialized feature that an application must explicitly enable.

FIPS impact: no
As the CMP code lives outside the FIPS module boundary, no FIPS modules
are affected by this CVE.

OpenSSL 4.0, 3.6, 3.5, 3.4, 3.0 are vulnerable to this issue.

OpenSSL 1.1.1 and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.

This issue was reported on 7 July 2026 by Ying Dong and independently by
Bhabani Sankar Das on 9 July 2026.
The fix has been developed by Daniel Kubec.

RPK Server Signature Algorithm Selection Can Dereference a Missing Certificate (CVE-2026-14457)
===============================================================================================

Severity: Low

Issue summary: In a server or client configuration with RFC7250 Raw Public Keys (RPKs)
enabled, and only the private key (with no associated certificate) configured locally,
a NULL pointer dereference may occur when the remote peer solicits raw public keys and
also sends the typically omitted "signature_algorithms_cert" TLS extension.

Impact summary: The impact is limited to a possible Denial of Service as a result of
an application abort, no data disclosure or remote command execution are possible.

CWE: CWE-476: NULL Pointer Dereference

Description: While a passing comment in sample code in the documentation suggests
that key-only RPK configurations are supported, the best-practice RPK configuration
is to always configure a corresponding certificate (possibly self-signed or
signed by any convenient CA).

When the private key is configured along with a matching certificate, the
"signature_algorithms_cert" extension is handled reliably even without the
fix, and peer clients or servers that don't support raw public keys may be
able to complete a TLS connection by pinning or verifying the corresponding
certificate or its public key.

Deployments that prefer to configure just a private key with no certificate
need to upgrade to an updated release as noted below.

FIPS impact: no

No FIPS modules are affected by this issue, as the SSL protocol implementation
is outside the OpenSSL FIPS module boundary.

OpenSSL 4.0, 3.6, 3.5, and 3.4 are vulnerable to this issue.

OpenSSL 3.0, 1.1.1, and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.

This issue was reported on 25 Jun 2026 by Filipe Casal (Trail of Bits) in
collaboration with OpenAI.
The fix has been developed by Viktor Dukhovni.

Excessive Memory Use Buffering DTLS Records for a Future Epoch (CVE-2026-54874)
===============================================================================

Severity: Low

Issue summary: Receiving a DTLS record for a future epoch while a handshake
is in progress causes OpenSSL to buffer far more memory than the record
itself requires.

Impact summary: A peer can use a small amount of network traffic to make an
OpenSSL DTLS endpoint retain a disproportionately large amount of memory,
which may lead to a Denial of Service.

CWE: CWE-405: Asymmetric Resource Consumption (Amplification)

Description: While a DTLS handshake is in progress, a peer may legitimately
have already moved on to the next epoch (for example, having sent its
ChangeCipherSpec and Finished messages) before the local endpoint has
processed the same transition, typically because of reordering on the
underlying UDP transport. OpenSSL buffers such early records so that they
can be processed once the local endpoint catches up.

Buffering a record currently retains the entire read buffer it arrived in,
which is sized to hold the largest possible DTLS record (around 16
kilobytes), rather than just the bytes that make up the record itself. Up
to 100 such records may be buffered per connection. As a result, a peer
that sends a stream of small forged records claiming to belong to the next
epoch can cause an OpenSSL DTLS endpoint to retain around 1.7 megabytes of
memory, despite sending only a small fraction of that amount of data over
the network.

An attacker therefore gains a memory amplification factor of around 1200,
and can multiply the effect across as many associations as it is able to
open, making this a remote memory exhaustion Denial of Service risk for
DTLS servers. Since the memory retained per connection remains bounded,
and any limit an application already places on the number of concurrent
associations also bounds the total exposure, this issue has been assessed
as Low severity.

FIPS impact: no

No FIPS modules are affected by this issue as the affected code is outside
the OpenSSL FIPS module boundary.

OpenSSL 4.0, 3.6, 3.5, 3.4, 3.0, 1.1.1 and 1.0.2 are vulnerable to this
issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.

Premium support customers only:
OpenSSL 1.1.1 users should upgrade to OpenSSL 1.1.1zi
OpenSSL 1.0.2 users should upgrade to OpenSSL 1.0.2zr

This issue was reported on 18 May 2026 by Amazon Web Services.
The fix has been developed by Matt Caswell.

Untrusted Sender DN Used as Format String in CMP Response Validation (CVE-2026-63073)
=====================================================================================

Severity: Low

Issue summary: OpenSSL CMP response validation passed an unexpected response
sender distinguished name directly as the format string to `ERR_raise_data()`.

Impact summary: A malicious or intercepted CMP endpoint can crash a CMP client
that enforces an expected sender or uses a pinned server certificate whose
subject becomes the default expected sender.

CWE: CWE-134: Use of Externally-Controlled Format String

Description: When validating a received CMP message, ossl_cmp_msg_check_update()
converts the peer-supplied sender distinguished name with X509_NAME_oneline()
and passes it directly as the format argument to ERR_raise_data(). Percent
characters survive the conversion, so a sender DN such as "CN=%s%n" reaches
BIO_vsnprintf() as an attacker-controlled format string with no matching variadic
arguments. This path is only reached when the caller configures an expected
sender or pins a server certificate, which is the normal configuration for a
CMP client validating server responses.

Since the attacker controls the format string but none of the variadic
arguments, such specifiers as %s and %n dereference or write through unrelated
stack contents and crash the client. The reliable consequence is a denial of
service, when the response comes from a malicious or intercepted CMP endpoint.
There is no controlled memory write, arbitrary-address read, or reliable path
to remote code execution.

FIPS impact: no

No FIPS modules are affected by this issue, as the CMP protocol
implementation is outside the OpenSSL FIPS module boundary.

OpenSSL 4.0, 3.6, 3.5, and 3.4 are vulnerable to this issue.

OpenSSL 3.0, 1.1.1, and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.

This issue was reported on 25 June 2026 by Filipe Casal (Trail of Bits) in
collaboration with OpenAI and independently by Brandon Luo on 22 July 2026
and TrendAI Zero Day Initiative on 14 August 2026.
The fix has been developed by Filipe Casal (Trail of Bits) in collaboration
with OpenAI.

CMP Indefinite Cache Growth of ExtraCerts (CVE-2026-63074)
==========================================================

Severity: Low

Issue summary: The OpenSSL Certificate Management Protocol (CMP) caches
additional certificates (extraCerts) sent in a CMP message, but never expunges
them (for instance if they are invalid).  If a server reuses an OSSL_CMP_CTX
frequently, this cache of extraCerts may grow unboundedly, and a malicious
client may flood a CMP server with requests driving this growth.

Impact summary: Users utilizing a CMP server that reuses a single OSSL_CMP_CTX
for the lifetime of a server process may observe unbounded memory growth in the
event a malicious client repeatedly sends requests containing unique extra
certificates, which may lead to OOM conditions.

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: If a remote user sends CMP messages to a server with a list of
extraCerts and the message is rejected, the extraCerts from the message remains
in the server contexts untrusted certificate stack.  This exposes servers with
long lived ctx objects to Denial of Service attacks in which an attacker sends
messages intending to be rejected with a large list of additional certificates
repeatedly, forcing the server to store them indefinitely.
   
The issue was fixed by removing the added extra certs if the message is
rejected, using the same method as when the context is configured to not do
caching at all.

FIPS impact: no
As the CMP code lives outside the FIPS module boundary, no FIPS
modules are affected by this CVE. 

OpenSSL 4.0, 3.6, 3.5, 3.4, and 3.0 are vulnerable to this issue.

OpenSSL 1.1.1 and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.

This issue was reported on June 29, 2026 by Pavol Zacik (Red Hat).
The fix has been developed by Neil Horman.

QUIC ACK-only Packet Retention Can Cause Memory Exhaustion (CVE-2026-63075)
===========================================================================

Severity: Low

Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly
sends ack-eliciting packets while not acknowledging ACK-only responses, the
QUIC stack can retain ACK-only packet metadata for the lifetime of the
connection.

Impact summary: A remote peer that can complete a QUIC handshake can
cause connection-scoped memory growth which may lead to Denial of Service
through memory exhaustion, especially with sustained traffic or many concurrent
QUIC connections.

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: When the OpenSSL QUIC stack sends an ACK-only packet,
there is no requirement by the QUIC protocol that the peer will acknowledge
that ACK-only packet (i.e. it is itself not ack-eliciting). However, the OpenSSL
implementation stores the metadata about the ACK frames regardless.
In and of itself that's ok, but if a malicious peer establishes a connection, and
then drives the connection such that ACK-only packets are forced from the 
OpenSSL implementation peer (i.e., by sending numerous PING frames),
and then withholding any subsequent acks for ack-eliciting data, like
legitimate data, said malicious peer can force inappropriate memory growth
on the OpenSSL peer, potentially leading to a Denial of Service.

The fix is to ensure that we account for the transmission of the ACK-only
packet in the packet histories high and low watermark without actually storing
the ACK-only packet metadata itself.

FIPS impact: no
The OpenSSL FIPS module is not affected as the QUIC code is
outside the FIPS module boundary.

OpenSSL 4.0, 3.6, 3.5, and 3.4 are vulnerable to this issue.

OpenSSL 3.0, 1.1.1 and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.

This issue was reported on 7 July 2026 by Opal Wright (Trail of Bits).
The fix has been developed by Neil Horman.

AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher() (CVE-2026-75803)
=============================================================================

Severity: Low

Issue summary: ChaCha20-Poly1305 and AES-OCB decryption with an empty
ciphertext can report success without verifying the supplied authentication
tag when the operation is finalized by calling the EVP_Cipher() function.

Impact summary: Applications calling EVP_Cipher() on an empty ciphertext and
expecting the call to check the AEAD tag may accept forged messages.

CWE: CWE-354: Improper Validation of Integrity Check Value

Description: The EVP_Cipher() API call for AEAD ciphers behaves like a one
shot encryption and decryption call. It also verifies the AEAD tag after the
decryption operation. However for AES-OCB and ChaCha20-Poly1305 ciphers
it skipped the AEAD tag verification when an empty ciphertext was passed to
the function. The callers of this function might believe that a successful
return indicates a valid AEAD tag for these ciphers, even when that has not
truly been validated in this case.

FIPS impact: no
The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this CVE
as the affected algorithms are not FIPS approved and thus not implemented
in the FIPS module.

OpenSSL 4.0, 3.6, 3.5, 3.4, and 3.0 are vulnerable to this issue.

OpenSSL 1.1.1 and 1.0.2 are not affected by this issue.

OpenSSL 4.0 users should upgrade to OpenSSL 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.

This issue was reported on 19 July, 2026 by Billy Brumley (Rochester
Institute of Technology).
The fix has been developed by Billy Brumley (Rochester Institute
of Technology).

General Advisory Notes
======================

URL for this Security Advisory:
https://openssl-library.org/news/secadv/20260825.txt

Note: the online version of the advisory may be updated with additional
details over time.

Only currently supported releases have been analysed. OpenSSL 3.1, 3.2 and 3.3
are out of support and have not been analysed.

For details of OpenSSL severity classifications please see:
https://openssl-library.org/policies/general/security-policy/