# Astral uv compromised emSign CA root certificate

Source: https://junglewise.ai/threats/pysec-2026-4321-uv-s-bundled-ca-store-trusts-an-emsign-root-whose-aeefabb5  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-20. Updated: 2026-10-22  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 4 · Published 2026-10-20

uv is a Python package manager that verifies downloads and dependencies using TLS encryption secured by a built-in list of trusted certificate authorities. An emSign root certificate authority whose intermediate signing keys have been compromised was included in uv's trust store, allowing an attacker with access to those keys to forge certificates for any website and intercept traffic. Upgrading to uv 0.13.4 or later removes this compromised root from the trust store.

Technologies: [Astral Uv](https://junglewise.ai/threats/technologies/astral-uv), [uv (PyPI)](https://junglewise.ai/threats/technologies/uv). Vendors: [Astral](https://junglewise.ai/threats/vendors/astral), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## 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?** Medium severity, with a CVSS score of 4, published 20 October 2026.

**Which products and versions are affected?** Astral Uv before 0.13.4; uv (PyPI) ECOSYSTEM:introduced=0,fixed=0.13.4.

**Is there a fix for This vulnerability?** Yes. uv (PyPI): upgrade to 0.13.4 or later. Until then: Users unable to upgrade immediately should use the --system-certs flag to rely on the operating system's certificate store, or use SSL_CERT_FILE or SSL_CERT_DIR to specify a custom certificate bundle that does not contain the compromised intermediates. 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 Astral Uv or uv (PyPI) 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

- uv (PyPI): upgrade to 0.13.4 or later

  ```sh
  pip install "uv>=0.13.4"
  ```


Users unable to upgrade immediately should use the --system-certs flag to rely on the operating system's certificate store, or use SSL_CERT_FILE or SSL_CERT_DIR to specify a custom certificate bundle that does not contain the compromised intermediates.

## Technical details

uv versions before 0.13.4 bundle the emSign ECC Root CA - G3 root certificate. Eight intermediate CA certificates issued by this root have been revoked by eMudhra due to private key compromise. An attacker with access to a compromised intermediate key can forge certificates that validate against uv's default CA bundle, enabling man-in-the-middle attacks on any hostname. The fix removes the root from the vendored bundle, following webpki-root-certs 1.0.10.

## Affected products

- Astral uv before 0.13.4

## Identifiers

- GHSA-hq85-5cpj-mr62
- PYSEC-2026-4321

## Timeline

- 2026-10-20: disclosed
- 2026-10-20: patched

## References

- [https://github.com/astral-sh/uv/security/advisories/GHSA-hq85-5cpj-mr62](https://github.com/astral-sh/uv/security/advisories/GHSA-hq85-5cpj-mr62)
- [https://github.com/certifi/python-certifi/security/advisories/GHSA-6q48-6c7w-9gw2](https://github.com/certifi/python-certifi/security/advisories/GHSA-6q48-6c7w-9gw2)

## Related threats

- [Astral uv arbitrary file deletion through RECORD entries](https://junglewise.ai/threats/duplicate-advisory-uv-vulnerable-to-arbitrary-file-deletion-through-b611c497)
- [Astral uv path traversal via RECORD entries](https://junglewise.ai/threats/cve-2026-114110-astral-uv-before-0-11-6-contains-a-path-traversal-vulnerability)
- [Astral uv path traversal via entry point names](https://junglewise.ai/threats/cve-2026-114109-uv-before-0-11-15-contains-a-path-traversal-vulnerability-that)
- [Astral uv path traversal in sdist tar extraction](https://junglewise.ai/threats/cve-2025-71437-astral-uv-before-0-8-22-contains-a-path-traversal-vulnerability)
- [uv bundled CA store trusts compromised emSign root](https://junglewise.ai/threats/uv-s-bundled-ca-store-trusts-an-emsign-root-whose-intermediate-ca-keys-38269068)