CVE-2026-54787Public exploitNetwork attack vector

Signature acceptance via unchecked expired-key timestamps

Published Jul 31, 2026 · Updated Jul 31, 2026

Improper key-expiration validation in Sigstore sigstore-go before 1.2.1 allows attackers to sign accepted bundles with expired key material. In pkg/verify/signed_entity.go, Verifier.Verify accepts verified timestamps for public-key-signed bundles without passing them to ValidAtTime against the ExpiringKey validity window. The flaw requires possession of expired self-managed key material and affects only certificate-free long-lived-key verification, not certificate-authority deployments.

CVSS severity3.1
Low
EPSS probability0.09%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper key-expiration validation in Sigstore sigstore-go before 1.2.1 allows attackers to sign accepted bundles with expired key material. In pkg/verify/signed_entity.go, Verifier.Verify accepts verified timestamps for public-key-signed bundles without passing them to ValidAtTime against the ExpiringKey validity window. The flaw requires possession of expired self-managed key material and affects only certificate-free long-lived-key verification, not certificate-authority deployments.

The record

CVE
CVE-2026-54787
Published
Jul 31, 2026
Updated
Jul 31, 2026
Vendor
Sigstore
Product
sigstore-go
Classifications
CWE-324, T1553.002
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Jul 31, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 31, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Sigstore · sigstore-goversion=< 1.2.1

Published CVSS scores

3.1SigstoreCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-324Use of a Key Past its Expiration Date
T1553.002Subvert Trust Controls: Code Signing

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo