7.8

CVE-2026-39853

osslsigncode has a Stack Buffer Overflow via Unbounded Digest Copy During Signature Verification

osslsigncode is a tool that implements Authenticode signing and timestamping. Prior to 2.12, A stack buffer overflow vulnerability exists in osslsigncode in several signature verification paths. During verification of a PKCS#7 signature, the code copies the digest value from a parsed SpcIndirectDataContent structure into a fixed-size stack buffer  (mdbuf[EVP_MAX_MD_SIZE], 64 bytes) without validating that the source length fits within the destination buffer. This pattern is present in the verification handlers for PE, MSI, CAB, and script files. An attacker can craft a malicious signed file with an oversized digest field in SpcIndirectDataContent. When a user verifies such a file with osslsigncode verify, the unbounded memcpy can overflow the stack buffer and corrupt adjacent stack state. This vulnerability is fixed in 2.12.
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EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.16% 0.058
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
security-advisories@github.com 7.8 1.8 5.9
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CWE-121 Stack-based Buffer Overflow

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

CWE-787 Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

https://github.com/mtrojnar/osslsigncode/security/advisories/GHSA-hx87-8754-xvh4
Vendor Advisory
https://github.com/mtrojnar/osslsigncode/commit/cbee1e723c5a8547302bd841ad9943ed8144db68
Patch
https://github.com/mtrojnar/osslsigncode/releases/tag/2.12
Product
Release Notes