CVE-2026-27851: Safe Filter Bug Enables SQL/LDAP Injection

The National Vulnerability Database has issued an advisory for CVE-2026-27851, a high-severity vulnerability (CVSS 7.4) where the ‘safe’ filter, when used with variable expansion, incorrectly extends its safety interpretation to subsequent pipelines on the same string. This flaw allows for unsafe data to be unescaped, opening the door for SQL or LDAP injection attacks, particularly concerning in authentication contexts.

This vulnerability fundamentally undermines the intended security controls of the ‘safe’ filter. Attackers can leverage this misinterpretation to bypass input sanitization, injecting malicious payloads that could lead to unauthorized access, data exfiltration, or system compromise. While no public exploits are currently known, the risk of injection attacks, especially those targeting authentication mechanisms, is significant and often leads to widespread impact.

Defenders should prioritize patching systems utilizing the ‘safe’ filter with variable expansion as soon as a fix becomes available. Until then, the National Vulnerability Database advises avoiding the use of the ‘safe’ filter in such configurations. Organizations must review their codebases and configurations to identify any instances where this pattern might be present, especially in critical authentication flows.