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Vulnerabilities

Vulnerability · CVE-2026-9256

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module.

Published May 22, 2026 · catalog updated Aug 25, 2026 · nginx open source

Check if you run it

No confirmed exploitation is on record for CVE-2026-9256. EPSS is 2.70%. Act only if a listed version of nginx open source is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.2
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
2.70%
Remediation
Advisory link
Affected products
cpe f5/dos · cpe f5/nginx open source · cpe f5/nginx plus · cpe redhat/discovery

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe f5/dosversion unspecified
  • cpe f5/nginx open source1.31.0
  • cpe f5/nginx plus37.0.0.1
  • cpe f5/nginx plusr32
  • cpe redhat/discoveryversion unspecified

How to fix CVE-2026-9256

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-9256. EPSS is 2.70%. Act only if a listed version of nginx open source is installed.

Which versions are affected?

Compare what you have installed with f5/nginx open source 1.31.0; f5/nginx plus 37.0.0.1; f5/nginx plus r32. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-122: Heap-based Buffer Overflow. EPSS 2.70%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Nginx security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 22, 2026 · NIST NVD

    Detected

    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 unauthent

  2. Aug 25, 2026 · NIST NVD

    Updated

    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 unauthent

Sources

  • CVE.orgVulnerability recordCVE-2026-9256

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-9256

    30-day exploitation probability 2.7%

    first.org
  • NIST NVDVulnerability recordCVE-2026-9256

    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 replac

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.