CVE-2026-25577 Emmett has an Unhandled CookieError Exception Causing Denial of Service
Unauthenticated attackers can cause denial of service by sending malformed Cookie headers that trigger unhandled exceptions in the Emmett framework.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-25577?
CVE-2026-25577 is a high-severity denial of service vulnerability in emmett-framework core, published on 10 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Emmett is a framework designed to simplify your development process. Prior to 1.3.11, the cookies property in mmett_core.http.wrappers.Request does not handle CookieError exceptions when parsing malformed Cookie headers. This allows unauthenticated attackers to trigger HTTP 500 errors and cause denial of service. This vulnerability is fixed in 1.3.11.
Which versions are affected by CVE-2026-25577?
3 open source packages ship an affected version, including emmett-core.
| Package | Affected | Fixed in |
|---|---|---|
emmett-core PyPI | All versions | 1.3.11 |
emmett-core PyPI | All versions | 1.3.11 |
emmett-core PyPI | All versions | 1.3.11 |
How do I fix CVE-2026-25577?
Upgrade emmett-core to 1.3.11 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-2026-25577 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-25577 exists.
Sources
Also known as GHSA-x6cr-mq53-cc76, PYSEC-2026-2469.