The vulnerability in apko versions earlier than 1.2.7 stems from a missing verification step for individual .apk packages. While the APKINDEX tarball is signed, the installer never compares the checksum of each downloaded package against the value recorded in the signed index. This oversight allows an attacker controlling the package source—be it a compromised mirror, an HTTP repository, or a poisoned CDN cache—to substitute a malicious package without detection. If the build process is fed such a package, the resulting OCI image will contain arbitrary code, effectively enabling the attacker to tamper with the image’s contents and potentially execute malicious binaries when the image is later used.

The affected product is Chainguard apko, a tool for creating OCI container images from apk packages. All releases before version 1.2.7 are impacted; the patch was introduced in release v1.2.7.

The CVSS score of 7.5 indicates high severity. EPSS data is not available, so the current exploitation probability is unknown, but the vulnerability is not listed in the CISA KEV catalog. An attacker only needs the ability to intercept or influence the package download path, which can be achieved remotely through a compromised mirror or CDN. Once the build in a trusted environment is attacked, the embedded malicious code will propagate with the newly built image, leading to widespread compromise if the image is deployed.