# CVE-2026-35537: Roundcube Webmail: Unsafe deserialization in the redis/memcache session handler

> Unauthenticated attackers can achieve arbitrary file write and potential code execution via unsafe deserialization in the Redis or Memcache session handler.

- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/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:** 3 Apr 2026
- **Updated:** 11 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-35537, GHSA-rxj3-rrwm-pj4r, UBUNTU-CVE-2026-35537, openSUSE-SU-2026:20586-1

## What is CVE-2026-35537?

CVE-2026-35537 is a low-severity unsafe deserialization vulnerability in Roundcube Webmail, published on 3 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. Unsafe deserialization in the redis/memcache session handler may lead to arbitrary file write operations by unauthenticated attackers via crafted session data.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-35537?

2 open source packages ship an affected version, including roundcube/roundcubemail. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `roundcube/roundcubemail` | Packagist | From 1.7-beta | 1.7-rc5 |
| `roundcube/roundcubemail` | Packagist | From 1.7-beta | 1.7-rc5 |
| `roundcubemail` | openSUSE:Leap 16.0 | All versions | 1.6.15-bp160.1.1 |

Products: Roundcube Webmail.

## How do I fix CVE-2026-35537?

Upgrade roundcube/roundcubemail to 1.7-rc5 or later.

## Is CVE-2026-35537 being exploited?

There is no known exploitation of CVE-2026-35537 in the wild and no public exploit code.

## Other vulnerabilities in Roundcube Webmail

- [CVE-2024-42009](https://insights.sbomify.com/CVE-2024-42009/): RoundCube Webmail Cross-Site Scripting (critical 9.3, exploited in the wild)
- [CVE-2025-68461](https://insights.sbomify.com/CVE-2025-68461/): RoundCube Webmail Cross-site Scripting (high 7.2, exploited in the wild)
- [CVE-2008-5619](https://insights.sbomify.com/CVE-2008-5619/): PHPMailer susceptible to arbitrary code execution (critical 10.0)
- [CVE-2024-37385](https://insights.sbomify.com/CVE-2024-37385/): Command injection in n/a (critical 9.8)
- [CVE-2024-42008](https://insights.sbomify.com/CVE-2024-42008/): Cross-site scripting in n/a (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35537 and fix it if it is affected.

What it is: CVE-2026-35537 is a low-severity unsafe deserialization vulnerability in Roundcube Webmail, published on 3 Apr 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-2026-35537 in the wild and no public exploit code.

Affected packages and fixed versions:
- roundcube/roundcubemail (Packagist): affected from 1.7-beta; fixed in 1.7-rc5
- roundcube/roundcubemail (Packagist): affected from 1.7-beta; fixed in 1.7-rc5

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-2026-35537/ (Markdown: https://insights.sbomify.com/CVE-2026-35537/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35537
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35537
- OSV: https://osv.dev/vulnerability/CVE-2026-35537

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35537/
Summaries are generated and may contain mistakes; the official description above is the record.