sigstore-go has a multi-log threshold bypass via single compromised log

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS

• CVE-2026-49834: 0.18% estimated exploitation activity in the next 30 days; percentile 7.71 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact What kind of vulnerability is it? Who is impacted? A verifier configured with WithTransparencyLog(N1) or WithSignedCertificateTimestamps(N1) expected defense-in-depth against the compromise of a single log instance. However, threshold counting counted verified witnesses per-entry or per-validation-path rather than per-log-authority. As a result, a single compromised transparency log could forge multiple entries with different indices, and a single compromised CT log could verify multiple times (either across multiple certificate chains or via multiple embedded SCTs), fully satisfying the multi-log threshold requirements and defeating the multi-log policy. Note that this does not affect Cosign, as Cosign sets a threshold of 1. Patches Has the problem been patched? What versions should users upgrade to? Upgrade to v1.1.5. Workarounds Is there a way for users to fix or remediate the vulnerability without upgrading? There is no workaround, beyond relying on trusted logs.

Published by the source

9 Jul 2026, 23:20 UTC

Last modified by the source

31 Jul 2026, 20:17 UTC

Source last checked

26 Oct 2026, 15:28 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9vcr-p3rj-q5q6

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# Patch Next advisory brief: CVE-2026-49834

Advisory: sigstore-go has a multi-log threshold bypass via single compromised log
IDs: CVE-2026-49834, GHSA-9vcr-p3rj-q5q6
Record: https://patchnext.com/advisories/cve-2026-49834 (revision 1, 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: Medium (CVSS 5.9)
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 1.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/sigstore/sigstore-go: affected <= 1.1.4; fixed in 1.2.0

## 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://github.com/advisories/GHSA-9vcr-p3rj-q5q6 (GitHub-reviewed advisory GHSA-9vcr-p3rj-q5q6 lists affected ranges: Go github.com/sigstore/sigstore-go >=0 <=1.1.4)

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