Apache APISIX: Failure to Sanitize Special Elements into a Different Plane
CVE-2026-31908 is a critical-severity failure to sanitize special elements into a different plane vulnerability in Apache APISIX from Apache, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache APISIX versions: 2.12.0 through 3.15.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.53% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Apisix to 3.16.0 or a later version.
- Read the advisory on lists.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache APISIX | 2.12.0 through 3.15.0 | Not stated |
| Apache | Apisix | 2.12.0 up to, but not including, 3.16.0 | 3.16.0 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by CISA (ADP).
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Failure to Sanitize Special Elements into a Different Plane
The product does not adequately filter user-controlled input for special elements with control implications.
How developers prevent this class of flaw
- Programming languages and supporting technologies might be chosen which are not subject to these issues.
- Utilize an appropriate mix of allowlist and denylist parsing to filter special element syntax from all input.
More Failure to Sanitize Special Elements into a Different Plane vulnerabilities (CWE-75)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- openwall.com/lists/oss-security/2026/04/14/3Mailing List, Third Party Advisory
Other vulnerabilities in Apache APISIX
- 7.0 High severity
- 7.8 High severity
- 8.2 High severity
- 8.1 High severity
- 7.5 High severity
- 7.5 High severity
Recent Failure to Sanitize Special Elements into a Different Plane vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 8.8 High severity
- 7.5 High severity
- 8.8 High severity
- 7.2 High severity
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