# CVE-2026-67351: Serendipity < 2.6.1 Authentication Bypass via Username Collision

> An authenticated Editor can escalate privileges to Administrator by exploiting a username collision vulnerability in Serendipity.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Jul 2026
- **Updated:** 31 Jul 2026
- **Also known as:** GHSA-v645-243f-jwgh

## What is CVE-2026-67351?

CVE-2026-67351 is a high-severity authentication bypass vulnerability in s9y Serendipity, published on 30 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Serendipity before 2.6.1 contains an authentication context confusion vulnerability where password validation and session loading operate independently without ensuring both use the same user record. An authenticated Editor can create a username collision with an Administrator account and obtain administrative privileges by logging in with their own password while the session loads the Administrator's account data.

Weakness: CWE-304 (Missing Critical Step in Authentication)

## Which versions are affected by CVE-2026-67351?


## How do I fix CVE-2026-67351?

No fix has been published for CVE-2026-67351 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-67351 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67351 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-67351 and fix it if it is affected.

What it is: CVE-2026-67351 is a high-severity authentication bypass vulnerability in s9y Serendipity, published on 30 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67351 exists.

Affected product: s9y Serendipity. 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-2026-67351/ (Markdown: https://insights.sbomify.com/CVE-2026-67351/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-67351
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-67351
- OSV: https://osv.dev/vulnerability/CVE-2026-67351

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-67351/
Summaries are generated and may contain mistakes; the official description above is the record.