GHSA-6q48-6c7w-9gw2 certifi bundles emSign root CAs with compromised intermediate CA keys
Attackers with compromised keys can issue valid certificates to intercept or modify TLS traffic for applications using the certifi library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is GHSA-6q48-6c7w-9gw2?
GHSA-6q48-6c7w-9gw2 is a vulnerability in certifi, published on 20 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Certifi versions before 2026.10.18 include the emSign ECC Root CA - G3 root certificate in their bundled CA store. Eight eMudhra intermediate CA certificates that chain to this root have compromised private keys and the CA has revoked them.
An attacker with one of the compromised keys can issue valid-looking certificates for any hostname. If the attacker is also on-path, they can intercept or modify TLS traffic from clients that trust the certifi bundle. Examples include requests, urllib3 and pip, and the Python.org macOS installer.
Certifi 2026.10.18 removed all emSign roots from the bundle. Certifi 2026.10.19 restored the emSign roots that are not affected. Upgrade to 2026.10.19 or later, and rebuild container images that vendor certifi.
Which versions are affected by GHSA-6q48-6c7w-9gw2?
3 open source packages ship an affected version, including certifi.
| Package | Affected | Fixed in |
|---|---|---|
certifi PyPI | From 2019.03.09 | 2026.10.18 |
certifi PyPI | From 2019.03.09 | 2026.10.18 |
certifi PyPI | From 2019.03.09 | 2026.10.19 |
How do I fix GHSA-6q48-6c7w-9gw2?
Upgrade certifi to a fixed version for your release line: 2026.10.18 or 2026.10.19.
Is GHSA-6q48-6c7w-9gw2 being exploited?
There is no known exploitation of GHSA-6q48-6c7w-9gw2 in the wild and no public exploit code.
Sources
Also known as PYSEC-2026-4320.