Openssl: >> Openssl >> 3.0.21 Security Vulnerabilities
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.
CVSS Score
9.1
EPSS Score
0.002
Published
2026-08-25
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.
CVSS Score
7.5
EPSS Score
0.006
Published
2026-08-25
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.
CVSS Score
5.9
EPSS Score
0.005
Published
2026-08-25
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.
CVSS Score
7.5
EPSS Score
0.013
Published
2026-08-25
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.
-- cut (non-publishing metadata for internal use) --
Reported by: Amazon Web Services
Fixed by: Matt Caswell
CVSS Score
7.5
EPSS Score
0.005
Published
2026-08-25
A bug exists in the way mod_ssl handled client renegotiations. A remote attacker could send a carefully crafted request that would cause mod_ssl to enter a loop leading to a denial of service. This bug can be only triggered with Apache HTTP Server version 2.4.37 when using OpenSSL version 1.1.1 or later, due to an interaction in changes to handling of renegotiation attempts.
CVSS Score
7.5
EPSS Score
0.591
Published
2019-01-30
mutt_ssl.c in mutt 1.5.19 and 1.5.20, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
CVSS Score
6.8
EPSS Score
0.011
Published
2009-10-23
mutt_ssl.c in mutt 1.5.16 and other versions before 1.5.19, when OpenSSL is used, does not verify the domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.
CVSS Score
6.8
EPSS Score
0.011
Published
2009-10-23
libraries/libldap/tls_o.c in OpenLDAP 2.2 and 2.4, and possibly other versions, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
CVSS Score
4.3
EPSS Score
0.033
Published
2009-10-23
Mutt 1.5.19, when linked against (1) OpenSSL (mutt_ssl.c) or (2) GnuTLS (mutt_ssl_gnutls.c), allows connections when only one TLS certificate in the chain is accepted instead of verifying the entire chain, which allows remote attackers to spoof trusted servers via a man-in-the-middle attack.
CVSS Score
6.8
EPSS Score
0.019
Published
2009-06-16
Page 1