Skip to content
Fencer Vulns
high 8.1

CVE-2026-8711 json

NGINX JavaScript vulnerability

published 2026-05-19 5 mo ago modified 2026-07-23 3 mo ago also EUVD-2026-30940

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
9.7%
EPSS 9.7% chance of exploitation in 30 days, percentile 95%
public exploits
0
none known

Summary

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, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Patch / fix

  • F5 NGINX JavaScript 0.9.9
  • libnginx-mod-js Debian 14 0.9.9-1

debian advisories DEBIAN-CVE-2026-8711

  • libnginx-mod-js Ubuntu Pro 26.04 LTS 0.9.4-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-8711

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • njs Alpine 3.24 0.9.9-r0
  • nginx Alpine 3.24 1.30.2-r1

alpine advisories ALPINE-CVE-2026-8711

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx Azure Linux 3.0 1.28.3-4

azure linux advisories AZL-87117

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-8711 updated cvss 8.1

nginx: NGINX JavaScript: Heap buffer overflow leading to denial of service and potential code execution via crafted HTTP requests.

  • Red Hat Enterprise Linux 8 nginx, nginx-mod-mail, nginx-filesystem, nginx-mod-stream, nginx-all-modules, nginx-mod-http-perl, +2 more Red Hat Enterprise Linux 9 nginx, nginx-core, nginx-mod-mail, nginx-filesystem, nginx-mod-stream, nginx-all-modules, +3 more Red Hat Enterprise Linux 10 nginx
    under investigation
  • Red Hat Hardened Images nginx
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
5 mo ago

Exploit prediction

9.69% chance of exploitation in the next 30 days, higher than 95% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • F5 NGINX JavaScript

Classification

Weakness
  • CWE-122 Heap-based Buffer Overflow

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.