Medium 5.5Published Apr 15, 2026

CVE-2026-39984Sigstore Timestamp Authority is a service for issuing RFC 3161 timestamps.

Updated under an hour ago (2026-10-19 07:30 UTC)

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It affects linuxfoundation sigstore_timestamp_authority. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for linuxfoundation sigstore_timestamp_authority

Exploited in the last 30 days

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.

CVSS: 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-295
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Not given
NVD analysis: Analyzed
Record last updated: Jun 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

linuxfoundation sigstore_timestamp_authority linuxfoundation:sigstore_timestamp_authority	before 2.0.6	NVD

References

https://github.com/sigstore/timestamp-authority/releases/tag/v2.0.6product, release-notes
https://github.com/sigstore/timestamp-authority/security/advisories/GHSA-xm5m-wgh2-rrg3mitigation, vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.