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

Low 3.7 Published 3 Apr 2026 Updated 11 Apr 2026

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

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

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

Which versions are affected by CVE-2026-35537?

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

Package	Affected	Fixed in
`roundcube/roundcubemail` Packagist	From `1.7-beta`	`1.7-rc5`
`roundcube/roundcubemail` Packagist	From `1.7-beta`	`1.7-rc5`

Linux distribution packages (1)

roundcubemail openSUSE:Leap 16.0 All versions 1.6.15-bp160.1.1

Products include Roundcube Webmail.

How do I fix CVE-2026-35537?

Upgrade roundcube/roundcubemail to 1.7-rc5 or later.

Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.

Is CVE-2026-35537 being exploited?

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

All Roundcube Webmail vulnerabilities

Sources

Also known as DEBIAN-CVE-2026-35537, GHSA-rxj3-rrwm-pj4r, UBUNTU-CVE-2026-35537, openSUSE-SU-2026:20586-1.