CVE-2026-25121: Chainguard.dev/apko Path Traversal Vulnerability

HIGH
Advisory Identifier: GHSA-5g94-c2wx-8pxw
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CVSS 7.5
CWE-23 CWE-22
Published
Advisory Summary

CVE-2026-25121 is a HIGH (CVSS 7.5) path traversal vulnerability (CWE-23: Relative Path Traversal) affecting Chainguard.dev/apko libraries in the Go ecosystem. The issue involves apko has a path traversal in apko dirfs which allows filesystem writes outside base. Remediation is available by upgrading affected packages to version 1.1.0.

CVE-2026-25121 at a Glance

CVE Identifier CVE-2026-25121
GHSA Identifier GHSA-5g94-c2wx-8pxw
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-23: Relative Path Traversal
Affected Product Chainguard.dev/apko
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-25121

To remediate this vulnerability, upgrade all affected Chainguard.dev/apko dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

chainguard.dev/apko fixed: 1.1.0 
Upgrade chainguard.dev/apko to 1.1.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for chainguard.dev/apko

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-25121, inspect your project dependencies for Chainguard.dev/apko:

inspect dependencies for chainguard.dev/apko

Analyze the terminal output to locate any version of Chainguard.dev/apko in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.1.0), 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-23: Relative Path Traversal, where the product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory. In Chainguard.dev/apko, 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

A Path Traversal vulnerability was discovered in apko's dirFS filesystem abstraction. An attacker who can supply a malicious APK package (e.g., via a compromised or typosquatted repository) could create directories or symlinks outside the intended installation root. The MkdirAll, Mkdir, and Symlink methods in pkg/apk/fs/rwosfs.go use filepath.Join() without validating that the resulting path stays within the base directory. **Fix:** Fixed by [d8b7887](https://github.com/chainguard-dev/apko/commit/d8b7887a968a527791b3c591ae83928cb49a9f14). Merged into release. **Acknowledgements** apko thanks Oleh Konko from [1seal](https://1seal.org/) for discovering and reporting this issue.

CVE-2026-25121 Affected Chainguard.dev/apko Versions

1 component(s)
Fixed Versions:
1.1.0
Product / Package Ecosystem Affected Versions Fixed Version
chainguard.dev/apko
golang/chainguard.dev/apko
Go
≥ 0.14.8
< 1.1.0
1.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/chainguard-dev/apko/security/advisories/GHSA-5g94-c2wx-8pxw
NVD — CVE-2026-25121 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25121
Security Fix Commit FIX COMMIT
https://github.com/chainguard-dev/apko/commit/d8b7887a968a527791b3c591ae83928cb49a9f14
Chainguard.dev/apko Source Repository REPOSITORY
https://github.com/chainguard-dev/apko

Frequently Asked Questions

What is CVE-2026-25121?
CVE-2026-25121 is a security vulnerability in Chainguard.dev/apko involving apko has a path traversal in apko dirFS which allows filesystem writes outside base under CWE-23: Relative Path Traversal.
Which Chainguard.dev/apko versions are affected?
Affected versions include releases prior to 1.1.0 across affected packages: chainguard.dev/apko.
What version fixes CVE-2026-25121?
Upgrading to 1.1.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is chainguard.dev/apko affected?
Yes, chainguard.dev/apko is affected in releases prior to 1.1.0. Upgrade your dependency to 1.1.0 or later.
What is the CVSS score of CVE-2026-25121?
CVE-2026-25121 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2026-25121?
CVE-2026-25121 is classified under CWE-23: Relative Path Traversal (The product uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory.).
How can I check Go dependencies for CVE-2026-25121?
Run the dependency tree command: 'inspect dependencies for chainguard.dev/apko'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5g94-c2wx-8pxw",
  "modified" : "2026-02-04T21:55:44Z",
  "published" : "2026-02-03T23:57:48Z",
  "aliases" : [ "CVE-2026-25121" ],
  "summary" : "apko has a path traversal in apko dirFS which allows filesystem writes outside base",
  "details" : "A Path Traversal vulnerability was discovered in apko's dirFS filesystem abstraction. An attacker who can supply a malicious APK package (e.g., via a compromised or typosquatted repository) could create directories or symlinks outside the intended installation root. The MkdirAll, Mkdir, and Symlink methods in pkg/apk/fs/rwosfs.go use filepath.Join() without validating that the resulting path stays within the base directory.\n\n**Fix:** Fixed by [d8b7887](https://github.com/chainguard-dev/apko/commit/d8b7887a968a527791b3c591ae83928cb49a9f14). Merged into release. \n\n**Acknowledgements**                                                                                                                                                                        \n                                                                                                                                                                                              \napko thanks Oleh Konko from [1seal](https://1seal.org/) for discovering and reporting this issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "chainguard.dev/apko"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.14.8"
      }, {
        "fixed" : "1.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/chainguard-dev/apko/security/advisories/GHSA-5g94-c2wx-8pxw"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-25121"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/chainguard-dev/apko/commit/d8b7887a968a527791b3c591ae83928cb49a9f14"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/chainguard-dev/apko"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-23" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-03T23:57:48Z",
    "nvd_published_at" : "2026-02-04T19:16:14Z"
  }
}