CVE-2026-9256: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module

This week

HIGH 8.1REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-9256 is a high-severity flaw (CVSS 8.1) affecting nginx open source, nginx plus, dos. 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 a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their

Why this priority

High severity
EPSS top 4%: very likely to be exploited
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	10.9% (top 4%)
CISA exploited list	No
Weakness	CWE-122
Published	2026-05-22
Last modified	2026-08-25

Publisher (CNA): F5 Networks · Vendor: f5

Last updated 2026-08-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-22 15:16 UTCPublished CVE record published
2026-08-25 13:19 UTCUpdated Record last modified

f5 nginx open source UPGRADE

Affected: >= 0.1.17 and <= 0.9.7 · >= 1.0.0 and < 1.30.2 · 1.31.0

Fixed in: 1.30.2

Safe to downgrade to: a release before 0.1.17

1. Check installed version

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

2. UPGRADE to 1.30.2 (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 0.1.17 (Debian / Ubuntu)

apt-cache madison nginx-open-source sudo apt install nginx-open-source=<VERSION_BEFORE_0.1.17> 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_0.1.17> 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: >= r33 and < r36 · 37.0.0.1 · r32 · r32 p1 · r32 p2 · r32 p3 · r32 p4 · r32 p5

Fixed in: r36

Safe to downgrade to: a release before 37.0.0.1

1. Check installed version

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

2. UPGRADE to 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 37.0.0.1 (Debian / Ubuntu)

apt-cache madison nginx-plus sudo apt install nginx-plus=<VERSION_BEFORE_37.0.0.1> 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_37.0.0.1> 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.

f5 dos UPGRADE

Affected: >= 4.3.0 and <= 4.7.0 · 4.9.0

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 < 2.6.2

Fixed in: 2.6.2

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 2.6.2 (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 < 5.4.3

Fixed in: 5.4.3

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 5.4.3 (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: >= 2.17.0 and < 2.22.1

Fixed in: 2.22.1

Safe to downgrade to: a release before 2.17.0

1. Check installed version

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

2. UPGRADE to 2.22.1 (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 2.17.0 (Debian / Ubuntu)

apt-cache madison nginx-instance-manager sudo apt install nginx-instance-manager=<VERSION_BEFORE_2.17.0> 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_2.17.0> 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.

Exact fixes by distribution

Fedora ELN · clash-meta · FIXED · 1.19.33-1.eln159 · FEDORA-2026-7dfb64c5e1 · source

sudo dnf upgrade --advisory=FEDORA-2026-7dfb64c5e1

Fedora 46 · vulkan-utility-libraries · FIXED · 1.4.363.0-1.fc46 · FEDORA-2026-994176daf5 · source

sudo dnf upgrade --advisory=FEDORA-2026-994176daf5

Debian 12 · nginx · FIXED · 1.22.1-9+deb12u8

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.22.1-9+deb12u8" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · nginx · FIXED · 1.26.3-3+deb13u6

sudo apt update && sudo apt install --only-upgrade nginx dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nginx)" ge "1.26.3-3+deb13u6" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · nginx · FIXED · nginx-1.26.3-6.el10_2.4

sudo dnf upgrade --advisory=RHSA-2026:29874 rpm -q nginx

RHEL 9 · nginx · FIXED · nginx-1.20.1-28.el9_8.3

sudo dnf upgrade --advisory=RHSA-2026:28973 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-r2

apk add --upgrade nginx apk info -v nginx

Alpine 3.23 · nginx · FIXED · nginx-1.28.3-r2

apk add --upgrade nginx apk info -v nginx

Alpine 3.24 · nginx · FIXED · nginx-1.30.2-r0

apk add --upgrade nginx apk info -v nginx

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1773 · source

sudo dnf update --advisory=ALAS2023-2026-1773

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: 3nou9h/CVE-2026-9256-Poc (3 stars)
GitHub PoC: W5M1n9/NGINX-ngx_http_rewrite_module-heap-buffer-overflow-CVE-2026-9256 (2 stars)
GitHub PoC: 06-ux/CVE-2026-9256-POC (1 stars)

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:28973] Important: nginx security update 2026-06-25
AlmaLinux Errata: [ALSA-2026:28212] Important: nginx:1.24 security update 2026-06-25
AlmaLinux Errata: [ALSA-2026:29151] Important: nginx:1.26 security update 2026-06-25

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-2026-9256?

nginx open source: upgrade to 1.30.2; nginx plus: upgrade to r36; dos: upgrade to newer than 4.7.0. Exact commands for each OS are on this page.

Is CVE-2026-9256 being exploited?

CVE-2026-9256 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-2026-9256 affect?

CVE-2026-9256 affects nginx open source, nginx plus, dos. 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 a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captur

How urgent is CVE-2026-9256?

Priority 62/100. High severity; EPSS top 4%: very likely to be exploited; 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-2026-42945 HIGH 8.1 UPGRADE UPGRADE NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module
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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