CVE-2026-31789

Technical Description

Issue summary: Converting an excessively large OCTET STRING value to

a hexadecimal string leads to a heap buffer overflow on 32 bit platforms.

Impact summary: A heap buffer overflow may lead to a crash or possibly

an attacker controlled code execution or other undefined behavior.

If an attacker can supply a crafted X.509 certificate with an excessively

large OCTET STRING value in extensions such as the Subject Key Identifier

(SKID) or Authority Key Identifier (AKID) which are being converted to hex,

the size of the buffer needed for the result is calculated as multiplication

of the input length by 3. On 32 bit platforms, this multiplication may overflow

resulting in the allocation of a smaller buffer and a heap buffer overflow.

Applications and services that print or log contents of untrusted X.509

certificates are vulnerable to this issue. As the certificates would have

to have sizes of over 1 Gigabyte, printing or logging such certificates

is a fairly unlikely operation and only 3

Remediation

Check the references section for vendor advisories and patches from openssl. Update openssl to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References