RCE in Zalando Skipper
CVE-2026-23742
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.
Vulnerability class: RCE (Remote Code Execution)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.005 (42.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 42.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: -0.000
Affected products
- Zalando Skipper — versions < 0.23.0
Weakness classification (CWE)
References
- github.com/zalando/skipper/security/advisories/GHSA-cc8m-98fm-rc9g (Exploit, Mitigation, Vendor Advisory)
- github.com/zalando/skipper/commit/0b52894570773b29e2f3c571b94b4211ef8fa714 (Patch)
- github.com/zalando/skipper/releases/tag/v0.23.0 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-23742?
- CVE-2026-23742 is a high-severity vulnerability in Zalando Skipper, classified under Code Injection. CVSS score: 8.8/10. Published 2026-01-16.
- How severe is CVE-2026-23742?
- High severity. CVSS v3 base score is 8.8 out of 10.