CVE-2026-25140 is a vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) found in the chainguard-dev apko tool, which is used to build and publish OCI container images from Alpine Linux APK packages. The vulnerability exists in the ExpandApk function within the pkg/apk/expandapk/expandapk.go file, where the tool expands .apk streams without enforcing limits on decompression size or resource usage. An attacker who controls or compromises an APK repository can serve a maliciously crafted .apk file that is small in compressed form but inflates into a very large tar archive upon decompression. This leads to excessive consumption of disk space and CPU resources on the build host, potentially causing build failures or denial of service conditions. The flaw affects apko versions from 0.14.8 up to but excluding 1.1.1, and has been addressed in version 1.1.1 by implementing appropriate decompression limits or resource controls. The vulnerability does not require authentication or user interaction, and the attack vector is via supply chain compromise or malicious APK repositories. Although no known exploits are reported in the wild, the high CVSS score of 7.5 reflects the significant impact on availability and ease of exploitation. This vulnerability highlights the risks of supply chain attacks in container build pipelines and the importance of validating and limiting resource usage during package expansion.

For European organizations, the impact of CVE-2026-25140 can be significant, particularly for those relying on apko for container image builds in CI/CD pipelines or production environments. Resource exhaustion on build hosts can lead to denial of service, delaying software delivery and potentially causing downtime in development or deployment workflows. Organizations using third-party or less trusted APK repositories are at higher risk of supply chain attacks that exploit this vulnerability. The disruption can affect availability of containerized applications, impacting business continuity and operational efficiency. Additionally, the consumption of excessive CPU and disk resources may increase operational costs and complicate incident response. While confidentiality and integrity are not directly impacted, the availability impact alone can be critical in environments with tight deployment schedules or automated pipelines. European sectors with high container adoption, such as finance, manufacturing, and technology, may face operational risks if this vulnerability is exploited.

To mitigate CVE-2026-25140, organizations should upgrade all instances of apko to version 1.1.1 or later, where the vulnerability has been patched. Additionally, organizations should implement strict validation and vetting of APK repositories used in their build pipelines to prevent supply chain compromise. Employing repository whitelisting, cryptographic signing verification, and integrity checks on APK packages can reduce the risk of malicious inputs. Monitoring resource usage during container builds and setting resource limits or quotas on build hosts can help detect and prevent resource exhaustion attacks. Integrating anomaly detection in CI/CD pipelines to flag unusually large decompression sizes or build failures can provide early warning. Finally, organizations should consider isolating build environments and using ephemeral build hosts to limit the blast radius of potential attacks.