CVE-2026-55149 Vouch Proxy: Unbounded Multipart Cookie Allocation DoS
An attacker can crash the Vouch Proxy authentication service by sending a crafted multipart cookie name, causing excessive memory allocation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55149?
CVE-2026-55149 is a high-severity denial of service vulnerability in vouch-proxy, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Vouch Proxy is an SSO and OAuth/OIDC login solution for Nginx using the auth_request module. Prior to 0.48.0, Cookie in pkg/cookie/cookie.go parses the total part count from an attacker-controlled multipart cookie name and passes the value to make([]string, numParts) without checking that the value is positive or reasonably bounded. Requests to /validate and /_external-auth-:id reach JWTCacheHandler in pkg/jwtmanager/jwtcache.go, FindJWT in pkg/jwtmanager/jwtmanager.go, and the vulnerable cookie reassembly before JWT validation, so no account or valid session is required. A cookie name such as VouchCookie_1of10000000000 causes an attempted slice allocation of roughly 160 GB and a fatal Go runtime out-of-memory condition, allowing one request to crash the authentication proxy and repeated requests to sustain unavailability. This vulnerability is fixed in 0.48.0.
Weakness: CWE-789
Which versions are affected by CVE-2026-55149?
3 open source packages ship an affected version, including github.com/vouch/vouch-proxy.
| Package | Affected | Fixed in |
|---|---|---|
github.com/vouch/vouch-proxy Go | All versions | 0.48.0 |
github.com/vouch/vouch-proxy Go | All versions | 0.48.0 |
github.com/vouch/vouch-proxy Go | All versions | 0.48.0 |
How do I fix CVE-2026-55149?
Upgrade github.com/vouch/vouch-proxy to 0.48.0 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-2026-55149 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55149 exists.
Sources
Also known as GHSA-qqff-5854-px68, GO-2026-6260.