Time-of-check Time-of-use (TOCTOU) Race Condition in Zammad - #VU153218
Published: October 3, 2026
Vulnerability identifier: #VU153218
CSH Severity: Medium
CVSS v4: 5.6 [CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-367
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to access internal-only network resources.
The vulnerability exists due to a time-of-check time-of-use race condition in the hostname safety check when validating and fetching an attacker-supplied URL. A remote attacker can manipulate DNS responses for a controlled domain to direct requests to internal addresses.
An administrator must configure the attacker-supplied URL, and exploitation depends on a DNS-timing race.
Affected software
Zammad
Remediation
Install security update from vendor's website.
Zammad - update to 7.1.3