Heap Buffer Over-read in OpenSSL ASN.1 Content Parsing
CVE-2026-34180 is a low-severity vulnerability in OpenSSL's ASN.1 decoder caused by integer truncation when parsing crafted DER-encoded ASN.1 primitive elements whose content length exceeds 2 gigabytes. On affected 64-bit Unix and Unix-like platforms, the oversized content length is mishandled during d2i_* decoding. In the worst case, the truncated length is interpreted as a request to scan binary content for a terminating zero byte, which can cause OpenSSL to read less than intended or beyond the end of the allocated input buffer. The issue affects applications that pass attacker-controlled ASN.1/DER data to functions such as d2i_X509(), d2i_PKCS7(), or other d2i_* decoding APIs. OpenSSL command-line tools are not affected because BIO-layer checks prevent the vulnerable code path. The issue does not affect 32-bit platforms, 64-bit Windows, or the OpenSSL FIPS modules in the 4.0, 3.6, 3.5, 3.4, and 3.0 branches.
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Impact, mitigation & remediation
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Impact
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Mitigation
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Remediation
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Exploits
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No public exploit code observed for this vulnerability.
Affected products & vendors
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
The version that knows your environment.
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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.