CVE-2026-31908: Apache APISIX: forward auth plugin allows header injection

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-14 · updated 2026-10-26
Weakness: CWE-75

Description

Header injection vulnerability in Apache APISIX. The attacker can take advantage of certain configuration in forward-auth plugin to inject malicious headers. This issue affects Apache APISIX: from 2.12.0 through 3.15.0. Users are recommended to upgrade to version 3.16.0, which fixes the issue.

Affected products

Apache Software Foundation Apache APISIX: from 2.12.0 before 3.16.0 — fixed in 3.16.0

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache APISIX 3.16.0. Check the vendor advisory for mitigations.

References

https://lists.apache.org/thread/sob643s5lztov7x579j8o0c444t36n6b
http://www.openwall.com/lists/oss-security/2026/04/14/3

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