CVE-2026-39853

Name	CVE-2026-39853
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
osslsigncode (PTS)	bullseye	2.1-1	vulnerable
	bullseye (security)	2.5-4~deb11u1+really2.9-1+deb11u2	vulnerable
	bookworm	2.5-4	vulnerable
	trixie	2.9-2	vulnerable
	forky, sid	2.13-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
osslsigncode	source	(unstable)	2.12-1

Notes

[trixie] - osslsigncode <no-dsa> (Minor issue)
[bookworm] - osslsigncode <no-dsa> (Minor issue)
[bullseye] - osslsigncode <postponed> (Minor issue)
https://github.com/mtrojnar/osslsigncode/security/advisories/GHSA-hx87-8754-xvh4
Fixed by: https://github.com/mtrojnar/osslsigncode/commit/cbee1e723c5a8547302bd841ad9943ed8144db68 (2.12)