CVE-2026-42945: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module

This week

HIGH 8.1REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-42945 is a high-severity flaw (CVSS 8.1) affecting dos, nginx gateway fabric, nginx ingress controller. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 sendin

Why this priority

High severity
EPSS top 1%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	68.0% (top 1%)
CISA exploited list	No
Weakness	CWE-122, CWE-131
Published	2026-05-13
Last modified	2026-10-26

Publisher (CNA): F5 Networks · Vendor: f5

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-13 16:16 UTCPublished CVE record published
2026-10-26 14:10 UTCUpdated Record last modified

f5 dos UPGRADE

Affected: >= 4.3.0 and <= 4.7.0 · 4.8.0

Fixed in: newer than 4.7.0

Safe to downgrade to: a release before 4.3.0

1. Check installed version

apt-cache policy dos || rpm -q dos || dos --version

2. UPGRADE to newer than 4.7.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade dos

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dos

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 4.3.0 (Debian / Ubuntu)

apt-cache madison dos sudo apt install dos=<VERSION_BEFORE_4.3.0> sudo apt-mark hold dos

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list dos sudo dnf downgrade dos-<VERSION_BEFORE_4.3.0> sudo dnf versionlock add dos

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

f5 nginx gateway fabric UPGRADE

Affected: >= 1.3.0 and <= 1.6.2 · >= 2.0.0 and <= 2.5.1

Fixed in: newer than 2.5.1

Safe to downgrade to: a release before 1.3.0

1. Check installed version

apt-cache policy nginx-gateway-fabric || rpm -q nginx-gateway-fabric || nginx-gateway-fabric --version

2. UPGRADE to newer than 2.5.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nginx-gateway-fabric

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nginx-gateway-fabric

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.3.0 (Debian / Ubuntu)

apt-cache madison nginx-gateway-fabric sudo apt install nginx-gateway-fabric=<VERSION_BEFORE_1.3.0> sudo apt-mark hold nginx-gateway-fabric

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nginx-gateway-fabric sudo dnf downgrade nginx-gateway-fabric-<VERSION_BEFORE_1.3.0> sudo dnf versionlock add nginx-gateway-fabric

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

f5 nginx ingress controller UPGRADE

Affected: >= 3.5.0 and <= 3.7.2 · >= 4.0.0 and <= 4.0.1 · >= 5.0.0 and <= 5.4.1

Fixed in: newer than 5.4.1

Safe to downgrade to: a release before 3.5.0

1. Check installed version

apt-cache policy nginx-ingress-controller || rpm -q nginx-ingress-controller || nginx-ingress-controller --version

2. UPGRADE to newer than 5.4.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nginx-ingress-controller

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nginx-ingress-controller

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.5.0 (Debian / Ubuntu)

apt-cache madison nginx-ingress-controller sudo apt install nginx-ingress-controller=<VERSION_BEFORE_3.5.0> sudo apt-mark hold nginx-ingress-controller

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nginx-ingress-controller sudo dnf downgrade nginx-ingress-controller-<VERSION_BEFORE_3.5.0> sudo dnf versionlock add nginx-ingress-controller

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

f5 nginx instance manager UPGRADE

Affected: >= 2.16.0 and <= 2.21.1

Fixed in: newer than 2.21.1

Safe to downgrade to: a release before 2.16.0

1. Check installed version

apt-cache policy nginx-instance-manager || rpm -q nginx-instance-manager || nginx-instance-manager --version

2. UPGRADE to newer than 2.21.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nginx-instance-manager

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nginx-instance-manager

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.16.0 (Debian / Ubuntu)

apt-cache madison nginx-instance-manager sudo apt install nginx-instance-manager=<VERSION_BEFORE_2.16.0> sudo apt-mark hold nginx-instance-manager

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nginx-instance-manager sudo dnf downgrade nginx-instance-manager-<VERSION_BEFORE_2.16.0> sudo dnf versionlock add nginx-instance-manager

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

f5 nginx open source UPGRADE

Affected: >= 0.6.27 and <= 1.30.0

Fixed in: newer than 1.30.0

Safe to downgrade to: a release before 0.6.27

1. Check installed version

apt-cache policy nginx-open-source || rpm -q nginx-open-source || nginx-open-source --version

2. UPGRADE to newer than 1.30.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nginx-open-source

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nginx-open-source

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.6.27 (Debian / Ubuntu)

apt-cache madison nginx-open-source sudo apt install nginx-open-source=<VERSION_BEFORE_0.6.27> sudo apt-mark hold nginx-open-source

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nginx-open-source sudo dnf downgrade nginx-open-source-<VERSION_BEFORE_0.6.27> sudo dnf versionlock add nginx-open-source

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

f5 nginx plus UPGRADE

Affected: >= r32 and <= r36

Fixed in: newer than r36

Safe to downgrade to: a release before r32

1. Check installed version

apt-cache policy nginx-plus || rpm -q nginx-plus || nginx-plus --version

2. UPGRADE to newer than r36 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nginx-plus

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nginx-plus

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before r32 (Debian / Ubuntu)

apt-cache madison nginx-plus sudo apt install nginx-plus=<VERSION_BEFORE_r32> sudo apt-mark hold nginx-plus

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nginx-plus sudo dnf downgrade nginx-plus-<VERSION_BEFORE_r32> sudo dnf versionlock add nginx-plus

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Ubuntu 24.04 · nginx · FIXED · 1.24.0-2ubuntu7.8

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.24.0-2ubuntu7.8" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 25.10 · nginx · FIXED · 1.28.0-6ubuntu1.3

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.28.0-6ubuntu1.3" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · nginx · FIXED · 1.18.0-6ubuntu14.11

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.18.0-6ubuntu14.11" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 20.04 · nginx · FIXED · 1.18.0-0ubuntu1.7+esm1

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.18.0-0ubuntu1.7+esm1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · nginx · FIXED · 1.22.1-9+deb12u7

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.22.1-9+deb12u7" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · nginx · FIXED · 1.26.3-3+deb13u5

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.26.3-3+deb13u5" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · nginx · FIXED · nginx-1.26.3-2.el10_1.2

sudo dnf upgrade --advisory=RHSA-2026:18063 rpm -q nginx

RHEL 10.0 Extended Update Support · nginx · FIXED · nginx-1.26.3-1.el10_0.9

sudo dnf upgrade --advisory=RHSA-2026:17790 rpm -q nginx

RHEL 9 · nginx · FIXED · nginx-1.20.1-24.el9_7.3

sudo dnf upgrade --advisory=RHSA-2026:18029 rpm -q nginx

RHEL 9.0 Update Services for SAP Solutions · nginx · FIXED · nginx-1.20.1-10.el9_0.4

sudo dnf upgrade --advisory=RHSA-2026:17791 rpm -q nginx

RHEL 9.2 Update Services for SAP Solutions · nginx · FIXED · nginx-1.20.1-14.el9_2.6

sudo dnf upgrade --advisory=RHSA-2026:17751 rpm -q nginx

Alpine 3.21 · nginx · FIXED · nginx-1.26.3-r1

apk add --upgrade nginx apk info -v nginx

Alpine 3.22 · nginx · FIXED · nginx-1.28.3-r1

apk add --upgrade nginx apk info -v nginx

Alpine 3.23 · nginx · FIXED · nginx-1.28.3-r1

apk add --upgrade nginx apk info -v nginx

Alpine 3.24 · nginx · FIXED · nginx-1.30.1-r0

apk add --upgrade nginx apk info -v nginx

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1714 · source

sudo dnf update --advisory=ALAS2023-2026-1714

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: cipherspy/CVE-2026-42945-POC (64 stars)
GitHub PoC: friparia/NGINX_RIFT_SCAN_CVE_2026_42945 (34 stars)
GitHub PoC: MateusVerass/nGixshell (27 stars)
Write-up: depthfirst.com/nginx-rift
Write-up: github.com/DepthFirstDisclosures/Nginx-Rift

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:19374] Critical: nginx security update 2026-05-26
AlmaLinux Errata: [ALSA-2026:19372] Critical: nginx:1.26 security update 2026-05-26
AlmaLinux Errata: [ALSA-2026:19371] Critical: nginx:1.24 security update 2026-05-26

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42945?

dos: upgrade to newer than 4.7.0; nginx gateway fabric: upgrade to newer than 2.5.1; nginx ingress controller: upgrade to newer than 5.4.1. Exact commands for each OS are on this page.

Is CVE-2026-42945 being exploited?

CVE-2026-42945 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42945 affect?

CVE-2026-42945 affects dos, nginx gateway fabric, nginx ingress controller. Severity is high (CVSS 8.1). 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 Expressi

How urgent is CVE-2026-42945?

Priority 68/100. High severity; EPSS top 1%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action; On your watchlist

Software pages

nginx vulnerabilities · F5 BIG-IP vulnerabilities · Perl vulnerabilities

Related CVEs

CVE-2026-40460 MEDIUM 6.5 UPGRADE UPGRADE When NGINX Plus or NGINX Open Source are configured to use the HTTP/3 QUIC module, an attacker may be able to
CVE-2026-40701 MEDIUM 4.8 UPGRADE UPGRADE NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssl_module module when the ssl_verify_cl
CVE-2026-42946 MEDIUM 6.5 UPGRADE UPGRADE A vulnerability exists in the ngx_http_scgi_module and ngx_http_uwsgi_module modules that may result in excess
CVE-2026-42934 MEDIUM 4.8 UPGRADE UPGRADE NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module

References

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