CVE-2026-8711: NGINX JavaScript has a vulnerability when the js_fetch_proxy directive is configured with at least one client-

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HIGH 8.1REMOTEWATCHLISTUPGRADE

CVE-2026-8711 is a high-severity flaw (CVSS 8.1) affecting njs. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NGINX JavaScript has a vulnerability when the js_fetch_proxy directive is configured with at least one client-controlled NGINX variable (for example, $http_*, $arg_*, $cookie_*) and a location invoking the ngx.fetch() operation from NGINX JavaScript. An unauthenticated attacker 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, atta

Why this priority

High severity
EPSS top 5%: 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	9.7% (top 5%)
CISA exploited list	No
Weakness	CWE-122
Published	2026-05-19
Last modified	2026-07-23

Publisher (CNA): F5 Networks · Vendor: f5

Last updated 2026-07-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-19 15:16 UTCPublished CVE record published
2026-07-23 20:10 UTCUpdated Record last modified

f5 njs UPGRADE

Affected: >= 0.9.4 and < 0.9.9

Fixed in: 0.9.9

Safe to downgrade to: a release before 0.9.4

1. Check installed version

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

2. UPGRADE to 0.9.9 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade njs

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 0.9.4 (Debian / Ubuntu)

apt-cache madison njs sudo apt install njs=<VERSION_BEFORE_0.9.4> sudo apt-mark hold njs

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

dnf --showduplicates list njs sudo dnf downgrade njs-<VERSION_BEFORE_0.9.4> sudo dnf versionlock add njs

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 46 · proftpd · FIXED · 1.3.9e-1.fc46 · FEDORA-2026-fc0d87d66e · source

sudo dnf upgrade --advisory=FEDORA-2026-fc0d87d66e

Ubuntu 24.04 · libnginx-mod-js · NOT AFFECTED

Ubuntu 25.10 · libnginx-mod-js · NOT AFFECTED

Debian 12 · libnginx-mod-js · NOT AFFECTED

Debian 13 · libnginx-mod-js · NOT AFFECTED

Alpine 3.24 · nginx · FIXED · nginx-1.30.2-r1

apk add --upgrade nginx apk info -v nginx

Alpine 3.24 · njs · FIXED · njs-0.9.9-r0

apk add --upgrade njs apk info -v njs

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-2026-8711?

njs: upgrade to 0.9.9. Exact commands for each OS are on this page.

Is CVE-2026-8711 being exploited?

CVE-2026-8711 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-2026-8711 affect?

CVE-2026-8711 affects njs. Severity is high (CVSS 8.1). NGINX JavaScript has a vulnerability when the js_fetch_proxy directive is configured with at least one client-controlled NGINX variable (for example, $http_*, $arg_*, $cookie_*) and a location invoking the ngx.fetch() operation from NGINX J

How urgent is CVE-2026-8711?

Priority 62/100. High severity; EPSS top 5%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

nginx vulnerabilities · F5 BIG-IP vulnerabilities

References

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