# CVE-2026-23742: Skipper arbitrary code execution through lua filters

> Attackers can execute arbitrary Lua code via inline filters in Skipper, potentially reading secrets and filesystem data.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 16 Jan 2026
- **Updated:** 16 Jan 2026
- **Also known as:** GHSA-cc8m-98fm-rc9g, GO-2026-4327

## What is CVE-2026-23742?

CVE-2026-23742 is a high-severity code injection vulnerability in zalando skipper, published on 16 Jan 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Skipper is an HTTP router and reverse proxy for service composition. The default skipper configuration before 0.23.0 was -lua-sources=inline,file. The problem starts if untrusted users can create lua filters, because of -lua-sources=inline , for example through a Kubernetes Ingress resource. The configuration inline allows these user to create a script that is able to read the filesystem accessible to the skipper process and if the user has access to read the logs, they an read skipper secrets. This vulnerability is fixed in 0.23.0.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-522 (Insufficiently Protected Credentials), CWE-250 (Execution with Unnecessary Privileges)

## Which versions are affected by CVE-2026-23742?

3 open source packages ship an affected version, including github.com/zalando/skipper. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/zalando/skipper` | Go | All versions | 0.23.0 |
| `github.com/zalando/skipper` | Go | All versions | 0.23.0 |
| `github.com/zalando/skipper` | Go | All versions | 0.23.0 |

Products: Zalando Skipper.

## How do I fix CVE-2026-23742?

Upgrade github.com/zalando/skipper to 0.23.0 or later.

## Is CVE-2026-23742 being exploited?

There is no known exploitation of CVE-2026-23742 in the wild and no public exploit code.

## Other vulnerabilities in zalando skipper

- [CVE-2022-38580](https://insights.sbomify.com/CVE-2022-38580/): Skipper vulnerable to SSRF via X-Skipper-Proxy (critical 9.8)
- [CVE-2026-24470](https://insights.sbomify.com/CVE-2026-24470/): Skipper Ingress Controller Allows Unauthorized Access to Internal Services via ExternalName (high 8.1)
- [CVE-2022-34296](https://insights.sbomify.com/CVE-2022-34296/): Query predicate bypass in Zalando Skipper (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23742 and fix it if it is affected.

What it is: CVE-2026-23742 is a high-severity code injection vulnerability in zalando skipper, published on 16 Jan 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23742 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/zalando/skipper (Go): affected all versions; fixed in 0.23.0
- github.com/zalando/skipper (Go): affected all versions; fixed in 0.23.0
- github.com/zalando/skipper (Go): affected all versions; fixed in 0.23.0

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-2026-23742/ (Markdown: https://insights.sbomify.com/CVE-2026-23742/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23742
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23742
- OSV: https://osv.dev/vulnerability/CVE-2026-23742

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23742/
Summaries are generated and may contain mistakes; the official description above is the record.