NGINX ngx_http_rewrite_module vulnerability
F5 · NGINX Plus
The flaw is a heap buffer overflow in the ngx_http_rewrite_module of F5's NGINX Plus and NGINX Open Source. It occurs when a rewrite directive is followed by a rewrite, if, or set directive that uses an unnamed PCRE capture (such as $1 or $2) with a replacement string containing a question mark. An unauthenticated remote attacker can trigger it by sending crafted HTTP requests, though it requires conditions outside the attacker's control; this can crash the NGINX worker process, and code execution is possible where ASLR is disabled or can be bypassed.
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.
- Exploited
- Yes, in VulnCheck KEV
- Reports
- 0
- Tactics
- 0/15
Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 3 days after disclosure. Public exploit code (PoC-in-GitHub) appeared 1 day after disclosure.
- Disclosedday 0
- Public exploit codePoC-in-GitHub+1 day
- First seen exploitedVulnCheck KEV evidence+3 days
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
No techniques linkedNo ATT&CK techniques are linked to this CVE yet. MITRE CTID has not mapped it, and no report passage in the corpus ties it to a technique.
What security researchers reported
Not named in any threat report yetAlso mentioned in 6 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Known_Cve | May 22, 202621 May 2026
- Known_Cve | May 21, 202620 May 2026
- Known_Cve | May 20, 2026 | Part 1/219 May 2026
- Known_Cve | May 19, 2026 | Part 1/218 May 2026
- Known_Cve | May 18, 2026 | Part 1/217 May 2026
- Known_Cve | May 17, 2026 | Part 1/216 May 2026