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Low, CVSS 3.1amended

sigstore-go fails to check signature timestamps against a signing key's validity period

CVE-2026-54787GHSA-wqqc-jjcq-vfxm

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/sigstore/sigstore-go 1.2.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
3.1 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
EPSS
  • CVE-2026-54787: 0.13% estimated exploitation activity in the next 30 days; percentile 2.90 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

sigstore-go fails to check signature timestamps against a signing key's validity period for self-managed long-lived keys without certificates. Impact To verify a bundle with a self-managed long-lived key, the key needs to be wrapped in an ExpiringKey type that implies expiration semantics: Despite the API contract, the validator does not check the bundle signing time against the validity window. Attackers that obtain expired key materials may be able to sign bundles with those materials that are accepted despite a configured expiry date. This issue only impacts the long-lived signing key workflow, and not standard deployments involving a certificate authority. Reproduction steps Start from a sigstore-go checkout: Apply the [patch] containing the test case and associated materials: Run the test: On vulnerable code, the test fails because verification succeeds even though the trusted ExpiringKey is not valid at the signed timestamp: [patch]:…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-wqqc-jjcq-vfxm

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6162

  3. Revision 1 · created ·

    Published from osv record GHSA-wqqc-jjcq-vfxm

Agent brief

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# Patch Next advisory brief: CVE-2026-54787

Advisory: sigstore-go fails to check signature timestamps against a signing key's validity period
IDs: CVE-2026-54787, GHSA-wqqc-jjcq-vfxm
Record: https://patchnext.com/advisories/cve-2026-54787 (revision 3, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/sigstore/sigstore-go 1.2.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/sigstore/sigstore-go: affected <= 1.2.0; fixed in 1.2.1

## Suggested inspection (read-only)
- Go github.com/sigstore/sigstore-go: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/sigstore/sigstore-go.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6162 (OSV record GO-2026-6162 lists affected ranges: Go github.com/sigstore/sigstore-go >=0 <1.2.1 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-wqqc-jjcq-vfxm (OSV record GHSA-wqqc-jjcq-vfxm lists affected ranges: Go github.com/sigstore/sigstore-go >=0 <1.2.1 (fixed))
- Verified: https://github.com/advisories/GHSA-wqqc-jjcq-vfxm (GitHub-reviewed advisory GHSA-wqqc-jjcq-vfxm lists affected ranges: Go github.com/sigstore/sigstore-go >=0 <=1.2.0)

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