Critical [CVE-2026-93479] vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format references the map's regex capture variables before referencing the map output variable
This critical-severity F5 advisory covers CVE-2026-93479 affecting NGINX Plus, NGINX Open Source.
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Summary
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format 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.
- NGINX Plus 37.1.0 before 37.1.0.1
- NGINX Plus 37.0.0 before 37.0.5.1
- NGINX Plus R36
- NGINX Plus R35
- NGINX Plus R34
- NGINX Plus R33
- NGINX Open Source 1.31.2 before 1.31.7
- NGINX Open Source 1.30.0 before 1.30.6
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
- 37.1.0.1
- 37.0.5.1
- 1.31.7
- 1.30.6
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
Mitigation
Upgrade to a fixed release: 37.1.0.1, 37.0.5.1, 1.31.7, 1.30.6. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 7 days ago·verify at source
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