# CVE-2026-42575: apko doesn't verify downloaded apk packages against APKINDEX checksum (package substitution possible)

> Attackers can substitute malicious APK packages during image builds because apko fails to verify downloaded package checksums against the signed index.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 May 2026
- **Updated:** 13 May 2026
- **Also known as:** CLEANSTART-2026-SY69656, GHSA-hcwr-pq9g-rq3m, GO-2026-5422, MINI-4rx3-rv43-cww4, MINI-7vj8-gqqv-55rj, MINI-8m8f-gpvp-f7x4

## What is CVE-2026-42575?

CVE-2026-42575 is a high-severity vulnerability in chainguard-dev apko, published on 9 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

apko allows users to build and publish OCI container images built from apk packages. Prior to version 1.2.7, apko verifies the signature on APKINDEX.tar.gz but never compares individually downloaded .apk packages against the checksum recorded in the signed index. The checksum is parsed and available via ChecksumString(), and the downloaded package control hash is computed, but the two values are never compared in getPackageImpl(). Mismatched packages are silently accepted. An attacker who can substitute download responses (compromised mirror, HTTP repository, poisoned CDN cache) can install arbitrary packages into built images. This issue has been patched in version 1.2.7.

Weakness: CWE-494 (Download of Code Without Integrity Check), CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-42575?

3 open source packages ship an affected version, including chainguard.dev/apko.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `chainguard.dev/apko` | Go | All versions | 1.2.7 |
| `chainguard.dev/apko` | Go | All versions | 1.2.7 |
| `chainguard.dev/apko` | Go | All versions | 1.2.7 |

## How do I fix CVE-2026-42575?

Upgrade chainguard.dev/apko to 1.2.7 or later.

## Is CVE-2026-42575 being exploited?

There is no known exploitation of CVE-2026-42575 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42575 and fix it if it is affected.

What it is: CVE-2026-42575 is a high-severity vulnerability in chainguard-dev apko, published on 9 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42575 in the wild and no public exploit code.

Affected packages and fixed versions:
- chainguard.dev/apko (Go): affected all versions; fixed in 1.2.7
- chainguard.dev/apko (Go): affected all versions; fixed in 1.2.7
- chainguard.dev/apko (Go): affected all versions; fixed in 1.2.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-42575/ (Markdown: https://insights.sbomify.com/CVE-2026-42575/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42575
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42575
- OSV: https://osv.dev/vulnerability/CVE-2026-42575

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42575/
Summaries are generated and may contain mistakes; the official description above is the record.