Critical [CVE-2026-42945] NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module
This critical-severity F5 advisory covers CVE-2026-42945 affecting NGINX Plus, NGINX Open Source.
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Summary
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when the rewrite directive is followed by a rewrite, if, or set directive and an unnamed Perl-Compatible Regular Expression (PCRE) capture (for example, $1, $2) with a replacement string that includes a question mark (?).
An unauthenticated attacker along with conditions beyond its 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. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
- NGINX Plus R36 before R36 P4
- NGINX Plus R32 before R32 P6
- NGINX Open Source 0.6.27 before 1.30.1
Official advisory · high-confidence parse· fetched 1 month ago·verify at source
- R36 P4
- R32 P6
- 1.30.1
Official advisory · high-confidence parse· fetched 1 month ago·verify at source
Mitigation
Upgrade to a fixed release: R36 P4, R32 P6, 1.30.1. 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 1 month ago·verify at source
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