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CVE-2026-42945

CRITICALCVSS 9.2/10EPSS 53.31%

Last modified

CVE-2026-42945 is a critical-severity vulnerability rated 9.2/10 on the CVSS scale. 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 (?). EPSS estimates a 53.31% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
8.1/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS 4.0
9.2/10

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
53.31%

98.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
F5Dos>= 4.3.0, <= 4.7.0
F5Dos4.8.0
F5Nginx Gateway Fabric>= 1.3.0, <= 1.6.2
F5Nginx Gateway Fabric>= 2.0.0, <= 2.5.1
F5Nginx Ingress Controller>= 3.5.0, <= 3.7.2
F5Nginx Ingress Controller>= 4.0.0, <= 4.0.1
F5Nginx Ingress Controller>= 5.0.0, <= 5.4.1
F5Nginx Instance Manager>= 2.16.0, <= 2.21.1
F5Nginx Open Source>= 0.6.27, <= 1.30.0
F5Nginx Plus>= r32, <= r36
F5Waf>= 4.9.0, <= 4.16.0
F5Waf>= 5.1.0, <= 5.8.0
F5Waf>= 5.9.0, <= 5.12.1

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-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) 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.
How severe is CVE-2026-42945?
CVE-2026-42945 has a CVSS score of 9.2/10 (CRITICAL severity). The EPSS model estimates a 53.31% probability of exploitation in the next 30 days.
How do I fix CVE-2026-42945?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-42945?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST