High

CVE-2026-91184 — NGINX Gateway Fabric vulnerability

Description NGINX Gateway Fabric has a vulnerability when it renders the spec.basic.realm (and spec.jwt.realm) field of a namespaced AuthenticationFilter verbatim, unescaped and unvalidated, into the shared data-plane nginx.conf as auth_basic "<realm>";. A namespaced authenticated attacker that configures AuthenticationFilter CRD to an HTTPRoute/GRPCRoute on a shared Gateway can craft a realm value that closes the quoted directive and the enclosing location {} block and injects arbitrary NGINX directives into that Gateway's data-plane config. Impact A remote authenticated attacker can send crafted requests to configure NGINX Gateway Fabric AuthenticationFilter CRD and may be able to read every co-located tenant's mounted secrets, SSRF via proxy_pass, reading the pod ServiceAccount token, or hijacking other tenants' routes. There is no data plane exposure; this is a control plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Published Oct 14, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: f5

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Nginx Gateway Fabric

CVSS base

8.8

High · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (F5 Nginx Gateway Fabric).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
F5	Nginx Gateway Fabric	≥ 2.4.0 and < 2.8.0	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
8.7	CVSS 4.0	High	—	—	f5sirt@f5.com via NIST National Vulnerability Database
8.7	CVSS 4.0	High	—	—	f5 via CVE Program (cve.org) e CISA ADP
8.8	CVSS 3.1	High	2.8	5.9	f5sirt@f5.com via NIST National Vulnerability Database
8.8	CVSS 3.1	High	—	—	GitHub, Inc. via GitHub Security Advisories
8.8	CVSS 3.1	High	—	—	f5 via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: f5sirt@f5.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-76

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · Received → Awaiting Analysis
Oct 14, 2026 · NIST National Vulnerability Database
Affected products added · f5/nginx gateway fabric
Oct 14, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 14, 2026
CVSS changed · 8.8
Oct 14, 2026 · NIST National Vulnerability Database
Source status changed · → Received
Oct 14, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 14, 2026 · NIST National Vulnerability Database
CVE published
Oct 14, 2026 · f5

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 14, 2026 – Oct 14, 2026
1× Official description updated · Oct 14, 2026 – Oct 14, 2026

References

3 on the record

my.f5.com/manage/s/article/K000162609
vendor-advisory, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-91184
GitHub Security Advisories
github.com/advisories/GHSA-8rxj-rxx8-xj47
GitHub Security Advisories

Elsewhere on this site

F5
every CVE for this vendor

CWE-76
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-96615 NGINX Gateway Fabric vulnerability 1d
High CVE-2026-60005 NGINX ngx_http_slice_module vulnerability Jul 15, 2026
Medium CVE-2026-60065 NGINX Plus ngx_stream_mqtt_filter_module vulnerability Jul 15, 2026
Medium CVE-2026-56434 NGINX ngx_http_ssi_module vulnerability Jul 15, 2026
High CVE-2026-42533 NGINX Map directive and Regex matching vulnerability Jul 15, 2026
High CVE-2026-50107 NGINX Gateway Fabric vulnerability Jun 17, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-91184 is "NGINX Gateway Fabric vulnerability", rated High. It affects Nginx Gateway Fabric (F5); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.