# CVE-2026-100351: kin-openapi: ValidationHandler security-requirement bypass via encoded-path operation confusion

> Attackers can bypass authentication in kin-openapi by exploiting path decoding mismatches between validation and routing, accessing protected endpoints without credentials.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Oct 2026
- **Updated:** 15 Oct 2026
- **Also known as:** CLEANSTART-2026-ZP83138, ECHO-5281-32ff-334d, GHSA-23vg-4cjm-66q5, MINI-339f-pcx8-mr64, MINI-372g-5w67-ghx3, MINI-46rp-3rvv-vj79, MINI-4hfg-2p9v-gr79, MINI-6xcc-8pmr-v92w, MINI-838c-5h5m-w2rx, MINI-9725-mw36-x76q, MINI-9gq7-qc8j-vrwj, MINI-f48g-7w3r-cf56, MINI-gq2w-w3m9-rjcq, MINI-jj94-75f2-9hr9, MINI-m8q7-h4cf-mpj7, MINI-rm8j-2vm2-hc9v, MINI-v5pc-9jg9-x3v4, MINI-vq7f-m5rf-qxj6, MINI-wj8f-xq45-xxvf, UBUNTU-CVE-2026-100351

## What is CVE-2026-100351?

CVE-2026-100351 is a high-severity authentication bypass vulnerability in getkin kin-openapi, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

kin-openapi is a Go project for handling OpenAPI files. From 0.144.0 until 0.147.0, openapi3filter.ValidationHandler validates an operation selected from decoded URL.Path while a downstream gorilla/mux router configured with UseEncodedPath can dispatch a different operation selected from URL.RawPath. When a public exact route and a protected parameterized route use the same method and overlap after decoding, an unauthenticated remote request containing an encoded path separator can be validated as public and then dispatched to the protected handler without invoking the configured AuthenticationFunc. The reachable path parameter is constrained to an encoded representation that decodes to the public literal route, and proxies that canonicalize the URI before forwarding prevent this specific mismatch. This issue is fixed in version 0.147.0.

Weakness: CWE-436 (Interpretation Conflict), CWE-289 (Authentication Bypass by Alternate Name)

## Which versions are affected by CVE-2026-100351?

2 open source packages ship an affected version, including github.com/getkin/kin-openapi.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/getkin/kin-openapi` | Go | From 0.144.0 | 0.147.0 |
| `github.com/getkin/kin-openapi` | Go | From 0.144.0 | 0.147.0 |

## How do I fix CVE-2026-100351?

Upgrade github.com/getkin/kin-openapi to 0.147.0 or later.

## Is CVE-2026-100351 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100351 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100351 and fix it if it is affected.

What it is: CVE-2026-100351 is a high-severity authentication bypass vulnerability in getkin kin-openapi, published on 15 Oct 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-2026-100351 exists.

Affected packages and fixed versions:
- github.com/getkin/kin-openapi (Go): affected from 0.144.0; fixed in 0.147.0
- github.com/getkin/kin-openapi (Go): affected from 0.144.0; fixed in 0.147.0

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-2026-100351/ (Markdown: https://insights.sbomify.com/CVE-2026-100351/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100351
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100351
- OSV: https://osv.dev/vulnerability/CVE-2026-100351

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100351/
Summaries are generated and may contain mistakes; the official description above is the record.