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CVE-2026-31789 is a heap-based buffer overflow in OpenSSL’s handling of hexadecimal conversion for excessively large ASN.1 OCTET STRING values on 32-bit platforms. The flaw occurs when untrusted X.509 certificate extension data, such as Subject Key Identifier or Authority Key Identifier values, is converted to a hexadecimal string. The required output buffer size is computed as the input length multiplied by three; on 32-bit systems this multiplication can overflow, causing allocation of an undersized heap buffer followed by out-of-bounds writes during conversion. The issue affects OpenSSL 3.0, 3.3, 3.4, 3.5, and 3.6 prior to the fixed releases. The vulnerable condition is outside the OpenSSL FIPS module boundary, and the FIPS modules for the affected branches are not impacted.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
18 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A specific vulnerability in OpenSSL addressed in Alpine Linux stable releases 3.20.10, 3.21.7, 3.22.4, and 3.23.4.
A heap buffer overflow in hexadecimal conversion in OpenSSL.
A heap buffer overflow in OpenSSL hexadecimal conversion functionality that may be exploitable when hex conversion APIs process untrusted input.
Heap buffer overflow in hexadecimal conversion in OpenSSL.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.