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Vulnerabilities

Vulnerability · CVE-2026-42945

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

Published May 13, 2026 · catalog updated Sep 10, 2026 · F5

Patch now

CVE-2026-42945 is in the CISA known-exploited catalog. Confirm F5 against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Severity
Critical9.2
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
3.40%
Remediation
Remediation guidance
Affected products
cpe f5/dos · cpe f5/nginx gateway fabric · cpe f5/nginx ingress controller · cpe f5/nginx instance manager · vendor F5 dos

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.

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/dos4.8.0
  • cpe f5/nginx gateway fabricversion unspecified
  • cpe f5/nginx ingress controllerversion unspecified
  • cpe f5/nginx instance managerversion unspecified
  • vendor F5 dosversion unspecified

How to fix CVE-2026-42945

What to do

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

Should you patch?

CVE-2026-42945 is in the CISA known-exploited catalog. Confirm F5 against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Compare what you have installed with 4.8.0. Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

What should an analyst verify?

CWE-122: Heap-based Buffer Overflow; CWE-131. EPSS 3.40%. The CISA KEV listing is the exploitation evidence. 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 13, 2026 · NIST NVD

    Detected

    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 it

  2. May 16, 2026 · CISA KEV

    Known exploited

    Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

  3. Sep 10, 2026 · NIST NVD

    Updated

    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 it

Sources

  • CVE.orgVulnerability recordCVE-2026-42945

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-42945

    30-day exploitation probability 3.4%

    first.org
  • NIST NVDVulnerability recordCVE-2026-42945

    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)

    nvd.nist.gov
  • VulnCheck KEVConfirmed exploitationCVE-2026-42945

    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)

    vulncheck.com

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.