# CVE-2026-118681: go-chi chi before 5.5.0 Authentication Bypass via SupressNotFound Middleware


- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-118681, GHSA-r83h-4mhv-9p8m, GHSA-rqrp-8cg2-5958, UBUNTU-CVE-2026-118681

## What is CVE-2026-118681?

CVE-2026-118681 is a medium-severity vulnerability in go-chi chi, published on 28 Oct 2026. 

### Official description

go-chi chi before 5.5.0 contains an authentication bypass in middleware.SupressNotFound, which calls Match with the live routing context and leaves a mounted router's parameter and child suffix in place for dispatch against the outer router. Unauthenticated attackers can request a mounted path whose suffix matches an outer public route, skipping the mounted authentication middleware and retrieving tenant-scoped data when that outer handler trusts the retained mount parameter.

Weakness: CWE-288 (Authentication Bypass Using an Alternate Path or Channel)

## Which versions are affected by CVE-2026-118681?


## How do I fix CVE-2026-118681?

No fix has been published for CVE-2026-118681 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-118681 being exploited?

There is no known exploitation of CVE-2026-118681 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-118681 and fix it if it is affected.

What it is: CVE-2026-118681 is a medium-severity vulnerability in go-chi chi, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-118681 in the wild and no public exploit code.

Affected product: go-chi chi. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-118681/ (Markdown: https://insights.sbomify.com/CVE-2026-118681/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-118681
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-118681
- OSV: https://osv.dev/vulnerability/CVE-2026-118681

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-118681/
Summaries are generated and may contain mistakes; the official description above is the record.