How severe is CVE-2026-42574?

CVE-2026-42574 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-42574?

CVE-2026-42574 affects the following packages: chainguard.dev/apko (Go). Ecosystems affected: Go.

How do I fix CVE-2026-42574?

Update chainguard.dev/apko to 1.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42574 is resolved across your whole dependency graph.

How do I detect CVE-2026-42574 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for chainguard.dev/apko, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42574 if there is no patch (or I can't update yet)?

Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Is CVE-2026-42574 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42574 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42574?

CVE-2026-42574 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 29th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42574?

CVE-2026-42574 is classified as Path Traversal (CWE-22), CWE-59 (CWE-59). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-42574 published, and has it been updated?

CVE-2026-42574 was published on May 9, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2026-42574 — apko

HIGHFix: chainguard-dev/apko@f5a96e1

CVE-2026-42574 is a high-severity (CVSS 7.5) Path Traversal vulnerability in chainguard.dev/apko. A fix is available for chainguard.dev/apko — see the affected versions and patch details below.

apko dirFS has a symlink-following path traversal that allows multiple entry points to escape the build root

Also known asGHSA-qq3r-w4hj-gjp6GO-2026-5589

Published

May 9, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
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-2026-42574.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs29th percentile — riskier than 29% of all scored CVEsHighest risk

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

1 pkg affected

🐹chainguard.dev/apko

Real-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

A crafted .apk could install a TypeSymlink tar entry whose target pointed outside the build root, and a subsequent directory-creation or file-write entry in the same or later archive could traverse that symlink to reach host paths the build user could write to. The root cause was the sanitizePath helper in pkg/apk/fs/rwosfs.go, which rejected only lexical .. traversal and did not resolve or refuse symlinks. Every disk-backed DirFS method that handed its caller-supplied path to a symlink-following stdlib call — ReadFile, WriteFile, Chmod, Chown, Chtimes, MkdirAll, Mkdir, and Mknod — was affected. The reachable primitive from a malicious APK during tar extraction is the MkdirAll / Mkdir / WriteFile chain via apko build-cpio and disk-backed consumers such as melange; the remaining sinks are reachable by direct callers of the pkg/apk/fs package. The in-memory tarfs install path used by apko build, apko publish, and apko build-minirootfs is not affected.

Patches

Fixed in apko v1.2.5 by #2187 / commit f5a96e1, which scopes all DirFS operations through a Go 1.24 *os.Root. The sanitizePath helper has been removed; *os.Root refuses traversal via .., absolute-target symlinks, relative-target symlinks, and hardlinks by construction. Regression tests in pkg/apk/apk/path_traversal_test.go cover each composite primitive.

Workarounds

No complete workaround. Operators running pre-1.2.5 apko (or downstream tools such as melange that embed pre-1.2.5 pkg/apk/fs) should upgrade. Consuming only APKs from trusted, signed sources reduces but does not eliminate exposure.

Resources

https://github.com/chainguard-dev/apko/pull/2187
https://github.com/chainguard-dev/apko/commit/f5a96e1299ac81c7ea9441705ec467688086f442
https://github.com/chainguard-dev/apko/releases/tag/v1.2.5
Related: GHSA-5g94-c2wx-8pxw (CVE-2026-25121) — prior lexical .. traversal fix

Credits

apko thanks Oleh Konko (@1seal from 1seal.org) for the initial report of the symlink-escape class, and to @Xh081iX for a follow-up set of reports covering additional reachable primitives (ReadFile, Chmod/Chown, Mknod, MkdirAll/Mkdir) that shaped the comprehensive fix.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`chainguard.dev/apko`	≥ 0.14.8&&< 1.2.5	1.2.5`go get chainguard.dev/apko@v1.2.5`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for chainguard.dev/apko, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update chainguard.dev/apko to 1.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42574 is resolved across your whole dependency graph.
Workarounds
Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

### Impact A crafted `.apk` could install a `TypeSymlink` tar entry whose target pointed outside the build root, and a subsequent directory-creation or file-write entry in the same or later archive could traverse that symlink to reach host paths the build user could write to. The root cause was the `sanitizePath` helper in `pkg/apk/fs/rwosfs.go`, which rejected only lexical `..` traversal and did not resolve or refuse symlinks. Every disk-backed `DirFS` method that handed its caller-supplied path to a symlink-following stdlib call — `ReadFile`, `WriteFile`, `Chmod`, `Chown`, `Chtimes`, `Mkdir