Infinite loop in Roundcube Webmail - #VU162697
Published: November 9, 2026
Vulnerability identifier: #VU162697
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-835
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service through excessive CPU consumption.
The vulnerability exists due to an unbounded loop in Roundcube Webmail's rcube_session::unserialize() function when processing a negative length token. A remote attacker can supply serialized session data containing a negative length token to trigger a CPU-consuming loop and disrupt service.
Affected software
Roundcube Webmail
Remediation
Install security update from vendor's website.
Roundcube Webmail - addressed in versions 1.6.21, 1.7.6