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MEDIUM severity

CVE-2021-25748 — ingress-nginx

MEDIUMFix: kubernetes/ingress-nginx#8623

CVE-2021-25748 is a medium-severity (CVSS 6.5) Improper Input Validation vulnerability in k8s.io/ingress-nginx. A fix is available for k8s.io/ingress-nginx — see the affected versions and patch details below.

Ingress-nginx `path` sanitization can be bypassed with newline character

Also known asGHSA-863x-868h-968x
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 31, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • 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-2021-25748.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk
0.00%0.40%0.80%1.19%0.1%0.7%May 26Aug 26Oct 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐹k8s.io/ingress-nginx

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

A security issue was discovered in ingress-nginx where a user that can create or update ingress objects can use a newline character to bypass the sanitization of the spec.rules[].http.paths[].path field of an Ingress object (in the networking.k8s.io or extensions API group) to obtain the credentials of the ingress-nginx controller. In the default configuration, that credential has access to all secrets in the cluster.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gok8s.io/ingress-nginxall versions1.2.1go get k8s.io/ingress-nginx@v1.2.1

Affected Products

1 product · 1 configurations
Application
ingress-nginxkubernetes
< 1.2.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for k8s.io/ingress-nginx, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update k8s.io/ingress-nginx to 1.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25748 is resolved across your whole dependency graph.

  3. Workarounds

    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

A security issue was discovered in ingress-nginx where a user that can create or update ingress objects can use a newline character to bypass the sanitization of the `spec.rules[].http.paths[].path` field of an Ingress object (in the `networking.k8s.io` or `extensions` API group) to obtain the credentials of the ingress-nginx controller. In the default configuration, that credential has access to all secrets in the cluster.
O3 Security · Impact-Aware SCA

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CVE-2021-25748: ingress-nginx — Fixed in 1.2.1