CVE-2026-23742: Github.com/zalando/skipper Skipper Is Vulnerable To Arbitrary Vulnerability
HIGHCVE-2026-23742 is a HIGH (CVSS 8.8) skipper is vulnerable to arbitrary vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Github.com/zalando/skipper libraries in the Go ecosystem. The issue involves skipper is vulnerable to arbitrary code execution through lua filters. Remediation is available by upgrading affected packages to version 0.23.0.
CVE-2026-23742 at a Glance
Security Impact
CVSS: 8.8
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
How to Fix CVE-2026-23742
To remediate this vulnerability, upgrade all affected Github.com/zalando/skipper dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/zalando/skipper to 0.23.0Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/zalando/skipperHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-23742, inspect your project dependencies for Github.com/zalando/skipper:
inspect dependencies for github.com/zalando/skipperAnalyze the terminal output to locate any version of Github.com/zalando/skipper in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.23.0), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-94: Improper Control of Generation of Code ('Code Injection'), where the product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. In Github.com/zalando/skipper, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-23742 Affected Github.com/zalando/skipper Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/zalando/skipper
|
Go |
< 0.23.0
|
0.23.0
|
References
Frequently Asked Questions
What is CVE-2026-23742?
Which Github.com/zalando/skipper versions are affected?
What version fixes CVE-2026-23742?
Is github.com/zalando/skipper affected?
What is the CVSS score of CVE-2026-23742?
What CWE is associated with CVE-2026-23742?
How can I check Go dependencies for CVE-2026-23742?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-cc8m-98fm-rc9g",
"modified" : "2026-01-16T21:57:03Z",
"published" : "2026-01-16T21:03:34Z",
"aliases" : [ "CVE-2026-23742" ],
"summary" : "Skipper is vulnerable to arbitrary code execution through lua filters",
"details" : "### Impact\n\nArbitrary code execution through [lua filters](https://opensource.zalando.com/skipper/reference/scripts/).\n\nThe default skipper configuration before v0.23 was `-lua-sources=inline,file`. \nThe 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.\n\nKubernetes example (vulnerability is not limited to Kubernetes)\n```lua\nfunction request(ctx, params)\n local file = io.open('/var/run/secrets/kubernetes.io/serviceaccount/token', 'r')\n if file then\n local token = file:read('*all')\n file:close()\n error('[EXFIL] ' .. token) -- Exfiltrate via error logs\n end\nend\n```\n\n### Patches\n\nhttps://github.com/zalando/skipper/releases/tag/v0.23.0 disables Lua by default.\n\n### Workarounds\n\nYou 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. \n\n### References\n\nhttps://opensource.zalando.com/skipper/reference/scripts/#enable-and-disable-lua-sources",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/zalando/skipper"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "0.23.0"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/zalando/skipper/security/advisories/GHSA-cc8m-98fm-rc9g"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-23742"
}, {
"type" : "WEB",
"url" : "https://github.com/zalando/skipper/commit/0b52894570773b29e2f3c571b94b4211ef8fa714"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/zalando/skipper"
}, {
"type" : "WEB",
"url" : "https://github.com/zalando/skipper/releases/tag/v0.23.0"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-250", "CWE-522", "CWE-94" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-01-16T21:03:34Z",
"nvd_published_at" : "2026-01-16T20:15:51Z"
}
}