# pypi-publish action improper certificate validation in Sigstore integration

Source: https://junglewise.ai/threats/pypi-publish-action-revocation-of-ca-in-the-chain-that-sigstore-uses-in-8146bd4a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

Severity: critical · Published 2026-10-30

The pypi-publish GitHub Action, which automates publishing Python packages to PyPI with cryptographic signing via Sigstore, bundled a revoked Certificate Authority (emSign) in its trust store. This revocation was not reflected in the action's bundled certificates, creating a window where an attacker holding a compromised private key for that CA could forge valid-looking signatures and inject malicious code into PyPI packages during the trusted publishing workflow.

Vendors: [GitHub Actions](https://junglewise.ai/threats/vendors/actions), [Pypa](https://junglewise.ai/threats/vendors/pypa).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Critical severity, published 30 October 2026.

**Which products and versions are affected?** pypa/gh-action-pypi-publish (GitHub Actions) <= 1.14.2; Pypa Gh-Action-Pypi-Publish 1.14.2 and earlier.

**Is there a fix for This vulnerability?** Yes: fixed in 1.14.3. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network.

**Am I affected?** Check whether you run pypa/gh-action-pypi-publish (GitHub Actions) or Pypa Gh-Action-Pypi-Publish 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

- Fixed in 1.14.3

## Technical details

The vulnerability is an improper certificate validation issue (CWE-295) where versions ≤1.14.2 bundled an outdated emSign root CA certificate through the certifi library, despite that CA being revoked by its issuer. Sigstore, which pypi-publish depends on for Trusted Publishing and Digital Attestations, relies on this TLS trust store for certificate chain validation. An attacker with the compromised CA private key could conduct a MITM attack or forge certificates to intercept or manipulate package publishing workflows, affecting confidentiality and integrity of published packages. The fix is available in version 1.14.3 and later.

## Affected products

- PyPA gh-action-pypi-publish 1.14.2 and earlier

## Timeline

- 2026-10-21: disclosed
- 2026-10-30: advisory

## References

- [https://github.com/pypa/gh-action-pypi-publish/security/advisories/GHSA-5xjx-3w67-w9x9](https://github.com/pypa/gh-action-pypi-publish/security/advisories/GHSA-5xjx-3w67-w9x9)