CVE-2026-56434: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssi_module module

This month

MEDIUM 6.5REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-56434 is a medium-severity flaw (CVSS 6.5) affecting nginx gateway fabric, nginx ingress controller, nginx plus. 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_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuration, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to cause a use-after-free in the NGINX worker process. This issue may lead to limite

Why this priority

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

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-416
Published	2026-07-15
Last modified	2026-08-10

Publisher (CNA): F5 Networks · Vendor: f5

Last updated 2026-08-10 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-15 15:16 UTCPublished CVE record published
2026-08-10 15:27 UTCUpdated Record last modified

f5 nginx gateway fabric UPGRADE

Affected: >= 1.3.0 and <= 1.6.2 · >= 2.0.0 and < 2.6.7

Fixed in: 2.6.7

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 2.6.7 (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 · >= 5.0.0 and < 5.5.3 · >= 2026-lts-r1 and < 2026-lts-r4 · 4.0.0 · 4.0.1

Fixed in: 5.5.3, 2026-lts-r4

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 5.5.3 (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 plus UPGRADE

Affected: >= 37.0.0.1 and < 37.0.3.1 · >= r33 and < r36 · r36 · r36 p1 · r36 p2 · r36 p3 · r36 p4 · r36 p5

Fixed in: 37.0.3.1, 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 37.0.3.1 (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 waf UPGRADE

Affected: >= 4.11.0 and <= 4.16.0 · >= 5.2.0 and <= 5.8.0 · >= 5.9.0 and < 5.13.4

Fixed in: 5.13.4

Safe to downgrade to: a release before 4.11.0

1. Check installed version

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

2. UPGRADE to 5.13.4 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade waf

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 4.11.0 (Debian / Ubuntu)

apt-cache madison waf sudo apt install waf=<VERSION_BEFORE_4.11.0> sudo apt-mark hold waf

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

dnf --showduplicates list waf sudo dnf downgrade waf-<VERSION_BEFORE_4.11.0> sudo dnf versionlock add waf

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-2026-56434?

nginx gateway fabric: upgrade to 2.6.7; nginx ingress controller: upgrade to 5.5.3, 2026-lts-r4; nginx plus: upgrade to 37.0.3.1, r36. Exact commands for each OS are on this page.

Is CVE-2026-56434 being exploited?

CVE-2026-56434 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-2026-56434 affect?

CVE-2026-56434 affects nginx gateway fabric, nginx ingress controller, nginx plus. Severity is medium (CVSS 6.5). NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuratio

How urgent is CVE-2026-56434?

Priority 42/100. Remotely exploitable, no login, no user action; On your watchlist

Software pages

nginx vulnerabilities · F5 BIG-IP vulnerabilities

Related CVEs

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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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