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CVE-2026-42945

79
FAUCET Score

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.

First published: May 13, 2026Last modified: May 21, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 4.3.0, <= 4.7.0CPE matchmatch criteria
cpe:2.3:a:f5:dos:*:*:*:*:*:nginx:*:*
4.8.0CPE matchmatch criteria
cpe:2.3:a:f5:dos:4.8.0:*:*:*:*:nginx:*:*
>= 1.3.0, <= 1.6.2CPE matchmatch criteria
cpe:2.3:a:f5:nginx_gateway_fabric:*:*:*:*:*:*:*:*
>= 2.0.0, <= 2.5.1CPE matchmatch criteria
cpe:2.3:a:f5:nginx_gateway_fabric:*:*:*:*:*:*:*:*
>= 3.5.0, <= 3.7.2CPE matchmatch criteria
cpe:2.3:a:f5:nginx_ingress_controller:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

9.2CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
HIGH
VS Integrity
HIGH
VS Availability
HIGH
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
61.47%
Probability of exploitation in next 30 days
EPSS Percentile
99.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.6147 is in the 99th percentile among its peer group of 8,918 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

microsoftpatch availablevia msrc
Product: 21341-17084Fixed in: 1.28.3-2
microsoftpatch availablevia msrc
Product: azl3 nginx 1.28.3-1 on Azure Linux 3.0Fixed in: 1.28.3-2
ubuntupatch availablevia ubuntu_usn
Product: nginx (jammy)Fixed in: 1.18.0-6ubuntu14.11
ubuntupatch availablevia ubuntu_usn
Product: nginx (noble)Fixed in: 1.24.0-2ubuntu7.8
ubuntupatch availablevia ubuntu_usn
Product: nginx (questing)Fixed in: 1.28.0-6ubuntu1.3
ubuntupatch availablevia ubuntu_usn
Product: nginx (resolute)Fixed in: 1.28.3-2ubuntu1.1

Vendor Advisories (2)

ubuntuUSN-8271-1

nginx vulnerability

May 14, 2026
microsoft2026-May/CVE-2026-42945Critical

NGINX ngx_http_rewrite_module vulnerability

May 12, 2026

References

access.redhat.com / errata/RHSA-2026:17417
access.redhat.com / errata/RHSA-2026:17751
access.redhat.com / errata/RHSA-2026:17752
access.redhat.com / errata/RHSA-2026:17753
access.redhat.com / errata/RHSA-2026:17790
access.redhat.com / errata/RHSA-2026:17791
access.redhat.com / errata/RHSA-2026:17792
access.redhat.com / errata/RHSA-2026:17793
access.redhat.com / errata/RHSA-2026:17794
access.redhat.com / errata/RHSA-2026:18029
access.redhat.com / errata/RHSA-2026:18041
access.redhat.com / errata/RHSA-2026:18063
access.redhat.com / errata/RHSA-2026:19159
access.redhat.com / errata/RHSA-2026:19371
access.redhat.com / errata/RHSA-2026:19372
access.redhat.com / errata/RHSA-2026:19374
access.redhat.com / errata/RHSA-2026:20442
access.redhat.com / errata/RHSA-2026:20444
access.redhat.com / errata/RHSA-2026:21275
access.redhat.com / errata/RHSA-2026:22382
access.redhat.com / errata/RHSA-2026:22383
access.redhat.com / errata/RHSA-2026:22388
access.redhat.com / errata/RHSA-2026:22389
access.redhat.com / errata/RHSA-2026:22390
access.redhat.com / errata/RHSA-2026:22393
access.redhat.com / errata/RHSA-2026:22394
access.redhat.com / errata/RHSA-2026:22396
access.redhat.com / security/cve/CVE-2026-42945
bugzilla.redhat.com / show_bug.cgi
security.access.redhat.com / data/csaf/v2/vex/2026/cve-2026-42945.json
depthfirst.com / nginx-rift
MitigationTechnical DescriptionThird Party Advisory
github.com / DepthFirstDisclosures/Nginx-Rift
ExploitThird Party Advisory
my.f5.com / manage/s/article/K000161019
MitigationVendor Advisory