# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-qqff-5854-px68, GO-2026-6260

## 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 (Memory Allocation with Excessive Size Value)

## Which versions are affected by CVE-2026-55149?

3 open source packages ship an affected version, including github.com/vouch/vouch-proxy.


| Package | Ecosystem | 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.

## Is CVE-2026-55149 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55149 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55149 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-55149 exists.

Affected packages and fixed versions:
- github.com/vouch/vouch-proxy (Go): affected all versions; fixed in 0.48.0
- github.com/vouch/vouch-proxy (Go): affected all versions; fixed in 0.48.0
- github.com/vouch/vouch-proxy (Go): affected all versions; fixed in 0.48.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55149/ (Markdown: https://insights.sbomify.com/CVE-2026-55149/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55149
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55149
- OSV: https://osv.dev/vulnerability/CVE-2026-55149

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55149/
Summaries are generated and may contain mistakes; the official description above is the record.