CVE-2026-42945

Description

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.

Why is this CVE high priority?

Possible remote code execution issue

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Patch details

References

• MITRE
• NVD
• Launchpad
• Debian

Related Ubuntu Security Notices (USN)

• USN-8271-1
• nginx vulnerability
• 14 May 2026
• USN-8375-1
• nginx vulnerabilities
• 3 June 2026

Other references

• https://www.cve.org/CVERecord?id=CVE-2026-42945
• https://www.openwall.com/lists/oss-security/2026/05/13/7
• https://depthfirst.com/research/nginx-rift-achieving-nginx-rce-via-an-18-year-old-vulnerability
• https://my.f5.com/manage/s/article/K000161019
• https://nginx.org/en/security_advisories.html