OpenSSL up to 4.0.0 symmAlg null pointer dereference

Summaryinfo

A vulnerability has been found in OpenSSL up to 3.0.20/3.4.5/3.5.6/3.6.2/4.0.0 and classified as problematic. This affects an unknown function. The manipulation of the argument symmAlg leads to null pointer dereference. This vulnerability is referenced as CVE-2026-42767. Remote exploitation of the attack is possible. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in OpenSSL up to 3.0.20/3.4.5/3.5.6/3.6.2/4.0.0. It has been rated as problematic. This issue affects an unknown part. The manipulation of the argument symmAlg with an unknown input leads to a null pointer dereference vulnerability. Using CWE to declare the problem leads to CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. Impacted is availability. The summary by CVE is:

Issue summary: An attacker-controlled CMP (Certificate Management Protocol) server could trigger a NULL pointer dereference in a CMP client application. Impact summary: A NULL pointer dereference causes a crash of the application and a Denial of Service. An attacker controlling a CMP server (or acting as a man-in-the-middle) could craft a CMP response containing a CRMF (Certificate Request Message Format) CertRepMessage with an EncryptedValue structure where the symmAlg field has an algorithm OID but no parameters field. When the OpenSSL CMP client processes this response, the NULL dereference occurs, causing a crash of the CMP client. Applications that process untrusted CMP/CRMF messages may be affected. The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

It is possible to read the advisory at openssl-library.org. The identification of this vulnerability is CVE-2026-42767 since 04/29/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/10/2026).

The vulnerability scanner Nessus provides a plugin with the ID 320340 (Linux Distros Unpatched Vulnerability : CVE-2026-42767), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 3.0.21, 3.4.6, 3.5.7, 3.6.3 or 4.0.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (320340). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Network Encryption Software

Name

• OpenSSL

Version

• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
• 3.0.12
• 3.0.13
• 3.0.14
• 3.0.15
• 3.0.16
• 3.0.17
• 3.0.18
• 3.0.19
• 3.0.20
• 3.4.0
• 3.4.1
• 3.4.2
• 3.4.3
• 3.4.4
• 3.4.5
• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3
• 3.5.4
• 3.5.5
• 3.5.6
• 3.6.0
• 3.6.1
• 3.6.2
• 4.0

License

• open-source

Website

• Product: https://www.openssl.org/

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Be aware that VulDB is the high quality source for vulnerability data.

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