Full Report
Kubernetes security advisory (AV26-260)
Analysis Summary
# Vulnerability: Ingress-Nginx Comment-Based Configuration Injection
## CVE Details
- **CVE ID:** CVE-2026-4342
- **CVSS Score:** Not explicitly provided in article (Typically High for configuration injections)
- **CWE:** CWE-94 (Improper Control of Generation of Code / Injection)
## Affected Systems
- **Products:** Kubernetes ingress-nginx
- **Versions:**
- Versions prior to 1.13.9
- Versions prior to 1.14.5
- Versions prior to 1.15.1
- **Configurations:** Systems utilizing Ingress objects where users have permissions to create or update Ingress resources and can manipulate annotations or fields that populate Nginx configuration comments.
## Vulnerability Description
This vulnerability allows an attacker with permissions to modify Ingress objects to inject arbitrary Nginx configuration code through specifically crafted comments. Due to improper sanitization of inputs that are placed within the `nginx.conf` as comments, an attacker can break out of the comment syntax and insert malicious directives. This can lead to unauthorized access to the Nginx process, information disclosure from other Ingress resources, or potential bypass of security controls (such as Lua-based plugins or WAFs).
## Exploitation
- **Status:** Vulnerability disclosed by vendor; exploitation status in the wild not specified in advisory.
- **Complexity:** Medium
- **Attack Vector:** Network (via Kubernetes API/Ingress resource manipulation)
## Impact
- **Confidentiality:** High (Access to sensitive configuration and traffic data)
- **Integrity:** High (Ability to modify routing and security logic)
- **Availability:** Medium (Potential for misconfiguration leading to DoS)
## Remediation
### Patches
Kubernetes has released the following patched versions to address this flaw:
- **v1.13.9**
- **v1.14.5**
- **v1.15.1**
### Workarounds
- Restrict "create" and "patch" permissions on Ingress resources using RBAC to trusted users only.
- Use Admission Controllers (such as Policy Engine like OPA or Kyberno) to validate and sanitize Ingress annotations to block suspicious characters or Nginx directives.
## Detection
- **Indicators of Compromise:** Review Kubernetes audit logs for unusual modifications to Ingress resources, specifically involving strange characters or unexpected Nginx syntax in annotations.
- **Detection methods:** Inspect the generated `nginx.conf` inside the ingress-nginx controller pods for unexpected directives appearing outside of standardized blocks or emerging from comment lines.
## References
- Vendor Advisory: [https[:]//discuss[.]kubernetes[.]io/t/security-advisory-cve-2026-4342-ingress-nginx-comment-based-nginx-configuration-injection/34349]
- Kubernetes Announcements: [https[:]//discuss[.]kubernetes[.]io/c/announcements/5]
- Canadian Centre for Cyber Security Bulletin: [https[:]//www[.]cyber[.]gc[.]ca/en/alerts-advisories/kubernetes-security-advisory-av26-260]