# CVE-2026-91939: Cotonti 1.0.0 Comments Plugin PHP Object Injection via ci Parameter

> Unauthenticated attackers can achieve code execution or database manipulation via PHP object injection in the Cotonti Comments plugin.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Sep 2026
- **Updated:** 24 Sep 2026
- **Also known as:** GHSA-xv9c-9hwm-jp8g

## What is CVE-2026-91939?

CVE-2026-91939 is a critical unsafe deserialization vulnerability in Cotonti, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Cotonti 1.0.0 Comments plugin passes the ci GET parameter to unserialize() without allowed_classes restriction, allowing unauthenticated attackers to instantiate arbitrary PHP classes with attacker-controlled properties. Attackers can exploit PHP object injection through crafted serialized payloads to trigger gadget chains and achieve database manipulation or code execution.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-91939?


## How do I fix CVE-2026-91939?

No fix has been published for CVE-2026-91939 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-91939 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-91939 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-91939 and fix it if it is affected.

What it is: CVE-2026-91939 is a critical unsafe deserialization vulnerability in Cotonti, 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-2026-91939 exists.

Affected product: Cotonti. 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-2026-91939/ (Markdown: https://insights.sbomify.com/CVE-2026-91939/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-91939
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-91939
- OSV: https://osv.dev/vulnerability/CVE-2026-91939

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-91939/
Summaries are generated and may contain mistakes; the official description above is the record.