f5 Nginx Gateway Fabric: heap buffer overflow can lead to remote code execution

Why it is Red

• CVSS 8.1 high
• Exploitation likely: EPSS 6.3% (top 6%)
• Remotely exploitable without logging in
• On your watchlist: nginx
• Named in a government or vendor bulletin

Government and vendor bulletins

• USN-8955-2: nginx vulnerabilities

References

• https://ubuntu.com/security/notices/USN-8955-2
• https://my.f5.com/manage/s/article/K000162097

Original 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.