# CVE-2021-25748: Ingress-nginx `path` sanitization can be bypassed with newline character

> Attackers can bypass path sanitization using newlines to steal controller credentials, potentially accessing all cluster secrets.

- **Severity:** High 7.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 May 2023
- **Updated:** 16 Jan 2025
- **Also known as:** GHSA-863x-868h-968x

## What is CVE-2021-25748?

CVE-2021-25748 is a high-severity vulnerability in Kubernetes ingress-nginx, published on 24 May 2023. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2021-25748?

2 open source packages ship an affected version, including k8s.io/ingress-nginx. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `k8s.io/ingress-nginx` | Go | All versions | 1.2.1 |
| `k8s.io/ingress-nginx` | Go | All versions | 1.2.1 |

Products: Kubernetes Ingress-Nginx.

## How do I fix CVE-2021-25748?

Upgrade k8s.io/ingress-nginx to 1.2.1 or later.

## Is CVE-2021-25748 being exploited?

There is no known exploitation of CVE-2021-25748 in the wild and no public exploit code.

## Other vulnerabilities in Kubernetes ingress-nginx

- [CVE-2026-3288](https://insights.sbomify.com/CVE-2026-3288/): ingress-nginx rewrite-target nginx configuration injection (high 8.8)
- [CVE-2022-4886](https://insights.sbomify.com/CVE-2022-4886/): Ingress-nginx `path` sanitization can be bypassed with `log_format` directive (high 8.8)
- [CVE-2023-5043](https://insights.sbomify.com/CVE-2023-5043/): Ingress nginx annotation injection causes arbitrary command execution (high 7.6)
- [CVE-2023-5044](https://insights.sbomify.com/CVE-2023-5044/): Code injection via nginx.ingress.kubernetes.io/permanent-redirect annotation (high 7.6)
- [CVE-2021-25745](https://insights.sbomify.com/CVE-2021-25745/): Ingress-nginx path can be pointed to service account token file (high 7.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25748 and fix it if it is affected.

What it is: CVE-2021-25748 is a high-severity vulnerability in Kubernetes ingress-nginx, published on 24 May 2023. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-25748 in the wild and no public exploit code.

Affected packages and fixed versions:
- k8s.io/ingress-nginx (Go): affected all versions; fixed in 1.2.1
- k8s.io/ingress-nginx (Go): affected all versions; fixed in 1.2.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-25748/ (Markdown: https://insights.sbomify.com/CVE-2021-25748/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25748
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25748
- OSV: https://osv.dev/vulnerability/CVE-2021-25748

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-25748/
Summaries are generated and may contain mistakes; the official description above is the record.