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Not in CISA KEV
HIGH severity

CVE-2026-104939

HIGH

CVE-2026-104939 is a high-severity (CVSS 7.5) CWE-303 vulnerability. No vendor fix is recorded yet; mitigation options are listed below.

Description NGINX Ingress Controller has a vulnerability when implementing an externalAuth policy for ingress. NGINX Ingress Controller may mishandle the HTTP response from an OAuth…

Published
Updated
Affected
—
Patched
—
Exploits
None indexed
Exploitation data as of Oct 15, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-104939.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-104939 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 389,824 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Description NGINX Ingress Controller has a vulnerability when implementing an externalAuth policy for ingress. NGINX Ingress Controller may mishandle the HTTP response from an OAuth IdP and allow an attacker to acquire unauthenticated access to protected paths before the proper external authentication can happen.

Impact This vulnerability may allow remote attackers

unauthenticated

access to protected

paths. There is no control plane exposure; this is a data plane issue only.

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

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2026-104939 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Description NGINX Ingress Controller has a vulnerability when implementing an externalAuth policy for ingress. NGINX Ingress Controller may mishandle the HTTP response from an OAuth IdP and allow an attacker to acquire unauthenticated access to protected paths before the proper external authentication can happen. Impact This vulnerability may allow remote attackers unauthenticated access to protected paths. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
O3 Security · Impact-Aware SCA

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CVE-2026-104939: High 7.5 severity