EUVD-2026-21290
GHSA-9qgc-pcpx-g38q
CVSS Vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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3Description
An integer underflow issue exists in wolfSSL when parsing the Subject Alternative Name (SAN) extension of X.509 certificates. A malformed certificate can specify an entry length larger than the enclosing sequence, causing the internal length counter to wrap during parsing. This results in incorrect handling of certificate data. The issue is limited to configurations using the original ASN.1 parsing implementation which is off by default.
Analysis
Integer underflow in wolfSSL's ASN.1 certificate parser allows remote attackers to trigger information disclosure and potential memory access violations when processing malformed X.509 certificates with oversized Subject Alternative Name extensions. The vulnerability affects wolfSSL versions up to 5.9.0 but only impacts systems using the non-default original ASN.1 parsing implementation; no public exploit code or active exploitation has been identified at time of analysis.
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