# CVE-2026-76834: b2evolution CMS 6.7.8 through 7.2.5 Object Injection via Negative Integer Array Key

> Unauthenticated attackers can achieve code execution in b2evolution CMS by bypassing validation checks to inject malicious serialized PHP objects.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:L/AT:P/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:** 17 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** GHSA-2vrr-cgr4-gfmm

## What is CVE-2026-76834?

CVE-2026-76834 is a critical unsafe deserialization vulnerability in b2evolution CMS, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

b2evolution CMS versions 6.7.8 through 7.2.5 contain an incomplete fix for CVE-2016-8901 where the serialized-array object check in param_check_serialized_array() fails to reject payloads with negative integer array keys. Unauthenticated attackers can submit crafted serialized PHP objects via POST requests to htsrv/call_plugin.php that bypass validation and reach unserialize(), instantiating arbitrary PHP objects with attacker-chosen properties that may enable code execution if suitable POP gadget chains exist.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-76834?


## How do I fix CVE-2026-76834?

No fix has been published for CVE-2026-76834 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-76834 being exploited?

There is no known exploitation of CVE-2026-76834 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76834 and fix it if it is affected.

What it is: CVE-2026-76834 is a critical unsafe deserialization vulnerability in b2evolution CMS, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-76834 in the wild and no public exploit code.

Affected product: b2evolution CMS. 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-2026-76834/ (Markdown: https://insights.sbomify.com/CVE-2026-76834/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76834
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76834
- OSV: https://osv.dev/vulnerability/CVE-2026-76834

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76834/
Summaries are generated and may contain mistakes; the official description above is the record.