CVE-2026-42934: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module

This month

MEDIUM 4.8REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-42934 is a medium-severity flaw (CVSS 4.8) 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_charset_module module. When charset, source_charset, and charset_map and proxy_pass with disabled buffering ("off") directives are configured, unauthenticated attackers can send requests that with conditions beyond the attackers' control to cause a heap buffer over-read in the NGINX worker process, leading to limited disclosure of memory or a restart. Note: Software version

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	4.8 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 46%)
CISA exploited list	No
Weakness	CWE-125
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 <= 2.6.0

Fixed in: newer than 2.6.0

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 2.6.0 (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 <= 5.4.2

Fixed in: newer than 5.4.2

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 5.4.2 (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 <= 2.22.0

Fixed in: newer than 2.22.0

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 2.22.0 (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: >= 0.3.50 and <= 0.9.7 · >= 1.0.0 and <= 1.30.0

Fixed in: newer than 1.30.0

Safe to downgrade to: a release before 0.3.50

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 0.3.50 (Debian / Ubuntu)

apt-cache madison nginx-open-source sudo apt install nginx-open-source=<VERSION_BEFORE_0.3.50> 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_0.3.50> 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.

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-2026-42934?

dos: upgrade to newer than 4.7.0; nginx gateway fabric: upgrade to newer than 2.6.0; nginx ingress controller: upgrade to newer than 5.4.2. Exact commands for each OS are on this page.

Is CVE-2026-42934 being exploited?

CVE-2026-42934 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-2026-42934 affect?

CVE-2026-42934 affects dos, nginx gateway fabric, nginx ingress controller. Severity is medium (CVSS 4.8). NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module. When charset, source_charset, and charset_map and proxy_pass with disabled buffering ("off") directives are configured, unauthenticated attackers c

How urgent is CVE-2026-42934?

Priority 40/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

nginx vulnerabilities · F5 BIG-IP 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

References

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