Vouch Proxy: Unbounded Multipart Cookie Allocation DoS (CVE-2026-55149) | HOL Guard CVE

High · CVSS 7.5CVE-2026-55149GHSA-QQFF-5854-PX68

Vouch Proxy: Unbounded Multipart Cookie Allocation DoS

Answer in brief

CVE-2026-55149 records a High severity (CVSS 7.5) vulnerability in Vouch Proxy: Unbounded Multipart Cookie Allocation DoS. The current sources do not mark it as known exploited. The current feed maps vouch/vouch-proxy (generic), github.com/vouch/vouch-proxy (go), github.com/vouch/vouch-proxy (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 15, 2026Updated Sep 15, 2026Source checked Sep 15, 2026First seen by HOL Aug 20, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps vouch/vouch-proxy (generic), github.com/vouch/vouch-proxy (go), github.com/vouch/vouch-proxy (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
vouch/vouch-proxygeneric	< 0.48.0	Not reported
github.com/vouch/vouch-proxygo	>=0 <0.48.0	0.48.0
github.com/vouch/vouch-proxygo	<=0.47.2	0.48.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for vouch/vouch-proxy, github.com/vouch/vouch-proxy, github.com/vouch/vouch-proxy.
Review the reported fix. Update github.com/vouch/vouch-proxy to 0.48.0; github.com/vouch/vouch-proxy to 0.48.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 20, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.