CVE-2026-79658 Ech0 before 5.0.1 Denial of Service via Accept-Language
An unauthenticated attacker can cause denial of service by sending large Accept-Language headers with underscores, triggering quadratic-time parsing in the Ech0 library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-79658?
CVE-2026-79658 is a high-severity denial of service vulnerability in lin-snow Ech0, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Ech0 before 5.0.1 does not impose any size or shape limit on the Accept-Language header processed by its i18n middleware, which runs on every HTTP request. The header is passed unfiltered to go-i18n's NewLocalizer, which internally calls golang.org/x/text/language.ParseAcceptLanguage. The CVE-2022-32149 mitigation in x/text caps '-' characters but not '_' characters, which the parser aliases to '-', allowing quadratic-time parsing to be triggered with a large header (up to Go's default 1 MiB) built from underscore separators. An unauthenticated attacker can send such requests to consume roughly 1.5 seconds of CPU each, and concurrent requests can saturate a multi-core server (denial of service).
Weakness: CWE-400
Which versions are affected by CVE-2026-79658?
How do I fix CVE-2026-79658?
No fix has been published for CVE-2026-79658 yet. Limit exposure of the affected software until one is available.
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-2026-79658 being exploited?
There is no known exploitation of CVE-2026-79658 in the wild and no public exploit code.
Sources
Also known as GHSA-j8jc-x8v7-x64g.