CVE-2026-39984

medium Red Hat
CVSS v3 Base Score
5.5
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
EPSS Score
0.0%
Exploitation probability in 30 days
Top 99% most likely to be exploited
Attack Characteristics
Attack Vector
Local
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Confidentiality
None
Integrity
High
Availability
None
Published: April 14, 2026 (86 days ago)
Last Modified: April 14, 2026
Vendor: Red Hat
Source: REDHAT

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.

CWE

CWE-295

Affected Products

Red Hat Advanced Cluster Security 4Red Hat Trusted Artifact SignerSecurity Profiles Operator

References

🔗 bugzilla.redhat.com 🔗 www.cve.org 🔗 nvd.nist.gov 🔗 github.com 🔗 github.com