sigstore CSRF possibility in OIDC authentication during signing

Exploitation

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

CVSS

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

EPSS

• CVE-2026-24408: 0.18% estimated exploitation activity in the next 30 days; percentile 7.42 (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.

Summary The sigstore-python OAuth authentication flow is susceptible to Cross-Site Request Forgery. Details OAuthSession creates a unique "state" and sends it as a parameter in the authentication request but the "state" in the server response seems not not be cross-checked with this value. Fix should be fairly trivial. Impact This should be low impact: A man-in-the middle attacker could trick a sigstore-python user into signing something with an identity controlled by the attacker (by returning the response to an authentication request they created). This would be quite confusing but not dangerous.

Published by the source

26 Jan 2026, 21:34 UTC

Last modified by the source

7 Jul 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:36 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hm8f-75xx-w2vr

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hm8f-75xx-w2vr

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# Patch Next advisory brief: CVE-2026-24408

Advisory: sigstore CSRF possibility in OIDC authentication during signing
IDs: CVE-2026-24408, GHSA-hm8f-75xx-w2vr
Record: https://patchnext.com/advisories/cve-2026-24408 (revision 2, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated (CVSS 0.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sigstore 4.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI sigstore: affected < 4.2.0; fixed in 4.2.0

## Suggested inspection (read-only)
- `python -m pip show sigstore`: prints the installed version. Run with the environment that serves production active.

## 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 sigstore.
- 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/GHSA-hm8f-75xx-w2vr (OSV record GHSA-hm8f-75xx-w2vr lists affected ranges: PyPI sigstore >=0 <4.2.0 (fixed))
- Verified: https://github.com/advisories/GHSA-hm8f-75xx-w2vr (GitHub-reviewed advisory GHSA-hm8f-75xx-w2vr lists affected ranges: PyPI sigstore >=0 <4.2.0)

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