CVE-2026-31789
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk16th percentile - higher than 16% of all known CVEs
Summary
Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer overflow on 32-bit platforms. This may cause a crash or potentially allow attacker-controlled code execution.
Risk Assessment
Organizations using OpenSSL on 32-bit systems are vulnerable to attacks via malicious X.509 certificates, potentially leading to application compromise.
Recommendation
Update OpenSSL to a patched version. Limit logging and display of certificates from untrusted sources.
Original NVD description (English source)
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 32 bit platforms are affected, this issue was assigned Low severity. 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.