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

Q: How do I fix CVE-2026-39984?

sigstore timestamp authority: upgrade to 2.0.6. Exact commands for each OS are on this page.

Q: Is CVE-2026-39984 being exploited?

CVE-2026-39984 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-39984 affect?

CVE-2026-39984 affects sigstore timestamp authority. Severity is medium (CVSS 5.5). 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 certif

Q: How urgent is CVE-2026-39984?

Priority 24/100. On your watchlist

Routine

MEDIUM 5.5WATCHLISTUPGRADE

CVE-2026-39984 is a medium-severity flaw (CVSS 5.5) affecting sigstore timestamp authority. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 atta

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.1% (top 99%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-04-15
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: linuxfoundation

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-15 04:17 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

linuxfoundation sigstore timestamp authority UPGRADE

Affected: < 2.0.6

Fixed in: 2.0.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sigstore-timestamp-authority || rpm -q sigstore-timestamp-authority || sigstore-timestamp-authority --version

2. UPGRADE to 2.0.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sigstore-timestamp-authority

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sigstore-timestamp-authority

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-39984?

sigstore timestamp authority: upgrade to 2.0.6. Exact commands for each OS are on this page.

Is CVE-2026-39984 being exploited?

CVE-2026-39984 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-39984 affect?

CVE-2026-39984 affects sigstore timestamp authority. Severity is medium (CVSS 5.5). 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 certif

How urgent is CVE-2026-39984?

Priority 24/100. On your watchlist

Related CVEs

CVE-2026-49835 MEDIUM 5.9 UPGRADE Sigstore Timestamp Authority is a service for issuing RFC 3161 timestamps

References

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