uv's bundled CA store trusts an emSign root whose intermediate CA keys are compromised
The source advisory has changed since this explanation was prepared. Check the current technical data and original advisory below.
By default, uv verifies TLS connections against a vendored copy of the webpki-root-certs bundle. Versions before 0.13.4 include the emSign ECC Root CA - G3 root. Eight eMudhra intermediate CA certificates that chain to that root have compromised private keys, and the CA has revoked them.
An attacker with one of the compromised keys can issue certificates that uv accepts for any hostname, which can be used to enable man-in-the-middle (MITM) attacks.
uv 0.13.4 removes the root from its vendored bundle, following webpki-root-certs 1.0.10.
What to do
Upgrade to 0.13.4 or later.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | uv | < 0.13.4 | 0.13.4 |
References
- 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://emudhra.we-have-a-problem.com
- https://github.com/astral-sh/uv
- https://groups.google.com/a/mozilla.org/g/dev-security-policy/c/0R3XLJL6FuE/m/0XofdebrAAAJ
- https://pypi.org/project/uv
- https://github.com/advisories/GHSA-hq85-5cpj-mr62
- CVSS vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-295- Platform
- Python (PyPI)
- Package
uv- Disclosed
- 20.10.2026
- Updated
- 21.10.2026 00:17
Sources and licenses · Edited or translated by DockRay; source rights and applicable licenses are retained.
OSV / GitHub Advisory Database - GHSA-hq85-5cpj-mr62 - CC BY 4.0
OSV / GitHub Advisory Database - PYSEC-2026-4321 - PyPA Advisory Database; CC BY 4.0
Vulnerability history: uv
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 08.2025 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- Medium 4
- Low 2
Disclosures per year
- 2025: 3
- 2026: 4
-
uv's bundled CA store trusts an emSign root whose intermediate CA keys are compromised this entry
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