Vulnerability Description
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| F5 | Nginx Gateway Fabric | >= 1.3.0, <= 1.6.2 |
| F5 | Nginx Ingress Controller | >= 3.5.0, <= 3.7.2 |
| F5 | Nginx Plus | >= 37.0.0.1, < 37.0.3.1 |
| F5 | Waf | >= 4.11.0, <= 4.16.0 |
Related Weaknesses (CWE)
References
- https://my.f5.com/manage/s/article/K000162097Vendor Advisory
FAQ
What is CVE-2026-42533?
CVE-2026-42533 is a vulnerability with a CVSS score of 8.1 (HIGH). A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map outp...
How severe is CVE-2026-42533?
CVE-2026-42533 has been rated HIGH with a CVSS base score of 8.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-42533?
Check the references section above for vendor advisories and patch information. Affected products include: F5 Nginx Gateway Fabric, F5 Nginx Ingress Controller, F5 Nginx Plus, F5 Waf.