CVEvulnerability

CVE-2026-39984

5.5 MEDIUM Published 2026-04-15 Modified 2026-10-26 Official page ↗
Status
Analyzed
Published
2026-04-15
Last modified
2026-10-26
Assigner
[email protected]
CVSS 3.1 ([email protected])
5.5 MEDIUM — CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Weaknesses
CWE-295

Description

Sigstore Timestamp Authority is a service for issuing RFC 3161 timestamps. Versions 2.0.5 and below contain an authorization bypass vulnerability in the VerifyTimestampResponse function. VerifyTimestampResponse correctly verifies the certificate chain signature, but the TSA-specific constraint checks in VerifyLeafCert uses the first non-CA certificate from the PKCS#7 certificate bag instead of the leaf certificate from the verified chain. An attacker can exploit this by prepending a forged certificate to the certificate bag while the message is signed with an authorized key, causing the library to validate the signature against one certificate but perform authorization checks against another. This vulnerability only affects users of the timestamp-authority/v2/pkg/verification package and does not affect the timestamp-authority service itself or sigstore-go. The issue has been fixed in version 2.0.6.

Affected configurations

• linuxfoundation sigstore timestamp authority (< 2.0.6)

Related

Weakness · CWE (1)

  • CWE-295 Improper Certificate Validation weakness

References