Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M
CVE-2026-55149Vouch Proxy: Unbounded Multipart Cookie Allocation DoS
High 7.5
In plain English
A high-severity security flaw in vouch-proxy from vouch. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 54% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/vouch/vouch-proxy | 0.48.0 | GHSA-qqff-5854-px68 |
| Go | github.com/vouch/vouch-proxy | 0.48.0 | GO-2026-6260 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| vouch | vouch-proxy | < 0.48.0 |
Weakness: CWE-789 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H