CVE-2026-54787: sigstore-go expired key usage in self-managed signing workflow

CVE-2026-54787 · Severity: low · CVSS 3.1 · Published 2026-07-31

sigstore-go is a software library used to verify the digital signatures of code and data to ensure they haven't been tampered with. A security flaw in the library fails to check if a signing key has expired when using specific long-lived, self-managed keys. This could allow an attacker who has obtained an old, expired key to create signatures that the system incorrectly trusts, potentially leading to the distribution of unauthorized or malicious software.

Technologies: github.com/sigstore/sigstore-go (Go). Vendors: Go, Sigstore.

Quick answers

Is CVE-2026-54787 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-54787 being exploited in the wild.
How severe is CVE-2026-54787?
Low severity, with a CVSS score of 3.1, published 31 July 2026.
Which products and versions are affected?
github.com/sigstore/sigstore-go (Go) <= 1.2.0, SEMVER:introduced=0,fixed=1.2.1; Sigstore-Go < 1.2.1, <= 1.2.0.
Is there a fix for CVE-2026-54787?
Yes. github.com/sigstore/sigstore-go (Go): upgrade to 1.2.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-54787 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-54787?
Check whether you run github.com/sigstore/sigstore-go (Go) or Sigstore-Go at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/sigstore/sigstore-go (Go): upgrade to 1.2.1 or later
    go get github.com/sigstore/sigstore-go@v1.2.1

Technical details

A vulnerability exists in sigstore-go's verification logic for self-managed long-lived signing keys that do not use certificates. When a key is wrapped in an ExpiringKey type to enforce expiration semantics, the library fails to compare the bundle's signing timestamp against the key's defined validity window. An attacker possessing expired key material could generate signed bundles that are incorrectly accepted as valid by the library. This issue specifically affects the long-lived signing key workflow and does not impact standard deployments using a Certificate Authority (CA). The issue is resolved in version 1.2.1 by ensuring timestamps are checked against the public key's validity window.

Affected products

  • sigstore sigstore-go < 1.2.1

Identifiers

  • CVE-2026-54787
  • GHSA-wqqc-jjcq-vfxm
  • GO-2026-6162

Timeline

  • 2026-06-09: patched: Fix committed and version 1.2.1 released.
  • 2026-07-31: disclosed: Advisory published.

References

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