# CVE-2026-34838: Group-Office: Authenticated Remote Code Execution via PHP Insecure Deserialization in `AbstractSettingsCollection`

> An authenticated attacker can achieve remote code execution by injecting a serialized object into settings, allowing arbitrary file writes on the server.

- **Severity:** Critical 10.0 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **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:** 2 Apr 2026
- **Updated:** 3 Apr 2026
- **Also known as:** GHSA-h22j-frrf-5vxq

## What is CVE-2026-34838?

CVE-2026-34838 is a critical unsafe deserialization vulnerability in Intermesh groupoffice, published on 2 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Group-Office is an enterprise customer relationship management and groupware tool. Prior to versions 6.8.156, 25.0.90, and 26.0.12, a vulnerability in the AbstractSettingsCollection model leads to insecure deserialization when these settings are loaded. By injecting a serialized FileCookieJar object into a setting string, an authenticated attacker can achieve Arbitrary File Write, leading directly to Remote Code Execution (RCE) on the server. This issue has been patched in versions 6.8.156, 25.0.90, and 26.0.12.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-34838?

It affects 1 product.


Products: Intermesh Group-Office.

## How do I fix CVE-2026-34838?

No fix has been published for CVE-2026-34838 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-34838 being exploited?

There is no known exploitation of CVE-2026-34838 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-34838 PoC (Proof of Concept) (github_poc): https://github.com/bamuwe/CVE-2026-34838

## Other vulnerabilities in Intermesh groupoffice

- [CVE-2026-27947](https://insights.sbomify.com/CVE-2026-27947/): Group-Office Vulnerable to Remote Code Execution (RCE) (critical 9.4)
- [CVE-2026-33755](https://insights.sbomify.com/CVE-2026-33755/): Authenticated SQL Injection in Contact/query addressBookIds filter (high 8.8)
- [CVE-2010-3428](https://insights.sbomify.com/CVE-2010-3428/): SQL injection in n/a (high 7.5)
- [CVE-2026-27832](https://insights.sbomify.com/CVE-2026-27832/): Group-Office Has Authenticated SQL Injection in advancedQueryData.comparator (high 7.1)
- [CVE-2025-48366](https://insights.sbomify.com/CVE-2025-48366/): GroupOffice's Blind Stored XSS in Phone Number Field Enables Forced Redirect and Unauthorized Actions (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34838 and fix it if it is affected.

What it is: CVE-2026-34838 is a critical unsafe deserialization vulnerability in Intermesh groupoffice, published on 2 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-34838 in the wild and no public exploit code.

Affected product: Intermesh groupoffice. 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-2026-34838/ (Markdown: https://insights.sbomify.com/CVE-2026-34838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34838
- OSV: https://osv.dev/vulnerability/CVE-2026-34838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34838/
Summaries are generated and may contain mistakes; the official description above is the record.