Buffer overflow in F5 Nginx Open Source
CVE-2026-42533
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 re…
Vulnerability class: Buffer Overflow
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
- F5 Nginx Open Source — versions 1.31.2, 0.9.6
- F5 Nginx Plus — versions 37.0.0.1, R36, R33
Weakness classification (CWE)
Public proof-of-concept exploits
References
- f5sirt@f5.com (vendor-advisory, patch)
Frequently asked questions
- What is CVE-2026-42533?
- CVE-2026-42533 is a high-severity vulnerability in F5 Nginx Open Source, classified under Heap-based Buffer Overflow. CVSS score: 8.1/10. Published 2026-07-15.
- How severe is CVE-2026-42533?
- High severity. CVSS v3 base score is 8.1 out of 10.
- Is CVE-2026-42533 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.