CVE-2026-9256

Description

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. 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. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

• How can I get the fixes?
• What do statuses mean?
• Patch details

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Patch details

References

• MITRE
• NVD
• Launchpad
• Debian

Related Ubuntu Security Notices (USN)

• USN-8354-1
• nginx vulnerabilities
• 1 June 2026
• USN-8375-1
• nginx vulnerabilities
• 3 June 2026

Other references

• https://www.cve.org/CVERecord?id=CVE-2026-9256
• https://my.f5.com/manage/s/article/K000161377
• http://www.openwall.com/lists/oss-security/2026/05/22/14