Openssl: >> Openssl >> 3.5.5 Security Vulnerabilities
Issue summary: When a delta CRL that contains a Delta CRL Indicator extension
is processed a NULL pointer dereference might happen if the required CRL
Number extension is missing.
Impact summary: A NULL pointer dereference can trigger a crash which
leads to a Denial of Service for an application.
When CRL processing and delta CRL processing is enabled during X.509
certificate verification, the delta CRL processing does not check
whether the CRL Number extension is NULL before dereferencing it.
When a malformed delta CRL file is being processed, this parameter
can be NULL, causing a NULL pointer dereference.
Exploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in
the verification context, the certificate being verified to contain a
freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and
an attacker to provide a malformed CRL to an application that processes it.
The vulnerability is limited to Denial of Service and cannot be escalated to
achieve code execution or memory disclosure. For that reason the issue was
assessed as Low severity according to our Security Policy.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue,
as the affected code is outside the OpenSSL FIPS module boundary.
CVSS Score
7.5
EPSS Score
0.009
Published
2026-04-07
Issue summary: An OpenSSL TLS 1.3 server may fail to negotiate the expected
preferred key exchange group when its key exchange group configuration includes
the default by using the 'DEFAULT' keyword.
Impact summary: A less preferred key exchange may be used even when a more
preferred group is supported by both client and server, if the group
was not included among the client's initial predicated keyshares.
This will sometimes be the case with the new hybrid post-quantum groups,
if the client chooses to defer their use until specifically requested by
the server.
If an OpenSSL TLS 1.3 server's configuration uses the 'DEFAULT' keyword to
interpolate the built-in default group list into its own configuration, perhaps
adding or removing specific elements, then an implementation defect causes the
'DEFAULT' list to lose its 'tuple' structure, and all server-supported groups
were treated as a single sufficiently secure 'tuple', with the server not
sending a Hello Retry Request (HRR) even when a group in a more preferred tuple
was mutually supported.
As a result, the client and server might fail to negotiate a mutually supported
post-quantum key agreement group, such as 'X25519MLKEM768', if the client's
configuration results in only 'classical' groups (such as 'X25519' being the
only ones in the client's initial keyshare prediction).
OpenSSL 3.5 and later support a new syntax for selecting the most preferred TLS
1.3 key agreement group on TLS servers. The old syntax had a single 'flat'
list of groups, and treated all the supported groups as sufficiently secure.
If any of the keyshares predicted by the client were supported by the server
the most preferred among these was selected, even if other groups supported by
the client, but not included in the list of predicted keyshares would have been
more preferred, if included.
The new syntax partitions the groups into distinct 'tuples' of roughly
equivalent security. Within each tuple the most preferred group included among
the client's predicted keyshares is chosen, but if the client supports a group
from a more preferred tuple, but did not predict any corresponding keyshares,
the server will ask the client to retry the ClientHello (by issuing a Hello
Retry Request or HRR) with the most preferred mutually supported group.
The above works as expected when the server's configuration uses the built-in
default group list, or explicitly defines its own list by directly defining the
various desired groups and group 'tuples'.
No OpenSSL FIPS modules are affected by this issue, the code in question lies
outside the FIPS boundary.
OpenSSL 3.6 and 3.5 are vulnerable to this issue.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.2 once it is released.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.6 once it is released.
OpenSSL 3.4, 3.3, 3.0, 1.0.2 and 1.1.1 are not affected by this issue.
CVSS Score
6.5
EPSS Score
0.004
Published
2026-03-13
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
0.599
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
0.031
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
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