CVE-2026-105768: chainguard-dev apko Numeric Truncation Error

Vulnerability summary

CVE-2026-105768 is a medium (CVSS 6.3) Numeric Truncation Error vulnerability in chainguard-dev apko. EPSS estimates a 0.30% chance of exploitation in the next 30 days, higher than 21.4% of scored vulnerabilities.

Timeline

1. 05-10-2026
   PublishedVulnerability first disclosed.
2. 06-10-2026
   Last modifiedVulnerability information updated.

Description

apko allows users to build and publish OCI container images built from apk packages. From version 0.2.0 to before version 1.4.5, UserEntry.Parse and GroupEntry.Parse in pkg/passwd read the UID and GID fields of /etc/passwd and /etc/group entries with strconv.Atoi and convert them to uint32 without a range check. On 64-bit platforms an out-of-range value such as 4294967296 (2^32) is truncated to 0, and negative values wrap. Because apko parses the passwd and group entries supplied by the packages it installs and writes them back into the image, an attacker who controls a package installed into the image can ship an entry that appears to declare an unprivileged UID or GID but is written into the built image as UID 0 or GID 0 (root). The truncated UID is also used when resolving the image's run-as user. This issue has been fixed in version 1.4.5.

• CWE-197Numeric Truncation ErrorTruncation errors occur when a primitive is cast to a primitive of a smaller size and data is lost in the conversion.