High severity · published May 13, 2026
CVE-2026-42945
NGINX ngx_http_rewrite_module vulnerability
8.1
CVSS
68%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)68.0% · higher than 99% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NO
NGINX Open Source · F5
0.6.27 before 1.30.1 · source: vendor, NVD
NP
NGINX Plus · F5
R36 before R36 P4; R32 before R32 P6 · source: vendor, NVD
DO
Dos · F5
4.3.0 through 4.7.0; 4.8.0 · source: NVD
NG
Nginx Gateway Fabric · F5
1.3.0 through 1.6.2; 2.0.0 through 2.5.1 · source: NVD
NI
Nginx Ingress Controller · F5
3.5.0 through 3.7.2; 4.0.0 through 4.0.1; 5.0.0 through 5.4.1 · source: NVD
NI
Nginx Instance Manager · F5
2.16.0 through 2.21.1 · source: NVD
WA
Waf · F5
4.9.0 through 4.16.0; 5.1.0 through 5.8.0; 5.9.0 through 5.12.1 · source: NVD
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: CISA
In the news
VulnerabilityHigh
Hitachi Energy e-mesh EMS
View CSAF
Summary
Hitachi Energy is aware of a buffer overflow vulnerability that affects e-mesh EMS product versions listed in this document. Successful exploitation of this vulnerability could lead to a buffer overflow condition, potentially resulting in application outages (denial of service) and possible arbitrary code execution. Please refer to the Recommended Immediate Actions for information about the mitigation/remediation.
The following versions of Hitachi Energy e-mesh EMS are affected:
Hitachi Energy e-mesh EMS 4.1.6, 4.4.2, 4.7.0
CVSS
Vendor
Equipment
Vulnerabilities
v3 8.1
Hitachi Energy
Hitachi Energy e-mesh EMS
Heap-based Buffer Overflow
Background
Critical Infrastructure Sectors: Energy
Countries/Areas Deployed: Worldwide
Company Headquarters Location: Switzerland
Vulnerabilities
Expand All +
CVE-2026-42945
NGINX Plus and NGINX Open Source used in e-mesh EMS 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 ...
Jul 7, 2026·CISA Advisories
VulnerabilityCritical
Attackers are exploiting critical NGINX vulnerability (CVE-2026-42945)
A critical NGINX vulnerability (CVE-2026-42945) disclosed last week is being exploited by attackers, VulnCheck security researcher Patrick Garrity revealed on Saturday. The vulnerability, dubbed NGINX Rift, can be reliably exploited to trigger a denial-of-service condition and can potentially allow for unauthenticated remote code execution, all achievable by sending a specially crafted HTTP request to a vulnerable NGINX instance. What is NGINX? NGINX is the most widely deployed web server and, as such, it’s one of … More →
The post Attackers are exploiting critical NGINX vulnerability (CVE-2026-42945) appeared first on Help Net Security .
May 18, 2026·Help Net Security
VulnerabilityCritical
Experts warn of active exploitation of critical NGINX flaw CVE-2026-42945
A critical NGINX flaw (CVE-2026-42945) is actively exploited, allowing crashes or possible code execution via malicious HTTP requests. A critical vulnerability in NGINX Plus and NGINX Open, tracked as CVE-2026-42945 (CVSS v4 score of 9.2), is already being actively exploited shortly after disclosure. “We’re seeing active exploitation of CVE-2026-42945 in F5 NGINX, a heap buffer […]
May 18, 2026·Security Affairs
VulnerabilityCritical
NGINX CVE-2026-42945 Exploited in the Wild, Causing Worker Crashes and Possible RCE
A newly disclosed security flaw impacting NGINX Plus and NGINX Open has come under active exploitation in the wild, days after its public disclosure, according to VulnCheck.
The vulnerability, tracked as CVE-2026-42945 (CVSS score: 9.2), is a heap buffer overflow in ngx_http_rewrite_module affecting NGINX versions 0.6.27 through 1.30.0. According to AI-native security company depthfirst, the
May 17, 2026·The Hacker News
VulnerabilityCritical
18-Year-Old NGINX Rewrite Module Flaw Enables Unauthenticated RCE
Cybersecurity researchers have disclosed multiple security vulnerabilities impacting NGINX Plus and NGINX Open, including a critical flaw that remained undetected for 18 years.
The vulnerability, discovered by depthfirst, is a heap buffer overflow issue impacting ngx_http_rewrite_module (CVE-2026-42945, CVSS v4 score: 9.2) that could allow an attacker to achieve remote code execution or cause a
May 14, 2026·The Hacker News
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42945
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-42945
Mitigation
https://my.f5.com/manage/s/article/K000161019
Mitigation
https://depthfirst.com/nginx-rift
Exploit
https://github.com/DepthFirstDisclosures/Nginx-Rift
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:17417
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:17751
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:17752
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