CVE-2026-42545 Granian: DoS via WSGI response header panic
A malicious WSGI application can cause a Denial of Service by returning invalid HTTP headers, triggering a worker process abort in Granian.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42545?
CVE-2026-42545 is a medium-severity denial of service vulnerability in emmett-framework granian, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Granian is a Rust HTTP server for Python applications. From 0.2.0 to 2.7.4, Granian aborts a worker process if a WSGI application returns an invalid HTTP response header name or value. The WSGI response conversion path uses .unwrap() on both the header name and header value constructors, so malformed output from the application becomes a process abort instead of a handled error. This vulnerability is fixed in 2.7.4.
Which versions are affected by CVE-2026-42545?
3 open source packages ship an affected version, including granian.
| Package | Affected | Fixed in |
|---|---|---|
granian PyPI | From 0.2.0 | 2.7.4 |
granian PyPI | From 0.2.0 | 2.7.4 |
granian PyPI | From 0.2.0 | 2.7.4 |
How do I fix CVE-2026-42545?
Upgrade granian to 2.7.4 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-42545 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42545 exists.
Sources
Also known as ECHO-929c-2ac9-d0a4, GHSA-f5p7-9fr5-8jmj, MINI-w9ph-v866-c555, PYSEC-2026-2502.