CVE-2026-47192 in kas
Summary
by MITRE • 08/14/2026
kas is a setup tool for bitbake based projects. Starting in version 4.8 and prior to version 5.3, kas checks out and processes repositories regarding configuration includes prior to validating signatures of those repositories. This may allow to replace on original repository with one under the control of an attacker under very specific conditions. First of all, the attacker must have gained control of a repository that a kas file of the victim is referencing. Furthermore, the following conditions must be fulfilled: the victim's kas configuration must include a configuration file from the attacked repository; the repository state is referenced by tag, and no commit ID is specified (this is triggering a warning, though); the key used for validating the tag or commit signature is stored as file in a repository; no fingerprint for the key is specified; and the `_source_dir` key must not be set by the victim when calling kas (e.g. by avoiding a local `.config.yaml`). Given these conditions, the attacker could modify the included kas configuration in way that the key used to validate the tag signature of the attacker's repository could be replaced by an attacker-chosen key. No other exploit possibilities have been identified so far, but this does not rule out that those may exist. All patches have been released along with kas version 5.3. As a workaround, pin the expected signature key via its fingerprint, also when storing it as file in a repository.
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Analysis
by VulDB Data Team • 08/14/2026
The kas tool represents a critical vulnerability in software supply chain security for bitbake-based projects, specifically within versions 4.8 through 5.2 where improper repository validation order creates exploitable conditions. This flaw resides in the sequence of operations during repository checkout and configuration processing, where kas performs repository inclusion handling before signature validation, creating a window for malicious manipulation. The vulnerability operates under specific but plausible attack conditions that could compromise the integrity of build environments.
The technical implementation of this vulnerability stems from kas's handling of repository signatures and configuration includes, which violates fundamental security principles of trust verification. When a kas configuration file references external repositories through include directives, the tool processes these includes before performing cryptographic signature validation on the target repositories. This ordering issue creates a race condition where an attacker who controls a referenced repository can manipulate the included configuration files to substitute legitimate signing keys with attacker-controlled ones. The vulnerability is classified as a software supply chain attack vector that directly relates to CWE-829 and CWE-494, representing inadequate validation of cryptographic signatures and improper handling of externally provided code.
The operational impact of this vulnerability extends beyond simple repository compromise, affecting the entire build integrity chain for projects relying on kas. Attackers who gain access to referenced repositories can effectively hijack the build process by replacing signature verification keys with their own, potentially leading to malicious code injection in downstream builds. The specific conditions required for exploitation include the attacker's control over a referenced repository, victim configuration that includes external files from that repository, and the absence of commit IDs in favor of tag references. Additionally, when signature keys are stored as repository files without specified fingerprints, and when victims don't set explicit source directories, the attack becomes viable through manipulation of the key inclusion chain.
This vulnerability demonstrates a classic case of insufficient input validation combined with improper security protocol ordering, aligning with ATT&CK technique T1583 for supply chain compromise and T1078 for valid accounts. The conditions required for exploitation create a narrow but dangerous attack surface where multiple security controls must fail simultaneously for successful compromise. The patch released in kas version 5.3 addresses this by enforcing proper signature validation order and requiring explicit key fingerprint specification, preventing the substitution attack vector entirely.
Mitigation strategies focus on strengthening configuration validation and key management practices within kas environments. Organizations should implement mandatory key fingerprint specification even when keys are stored within repositories, as this prevents the substitution attacks that rely on implicit trust relationships. The workaround of pinning expected signature keys via fingerprints represents a defensive measure against this specific vulnerability while maintaining operational functionality. Security teams should also implement repository access controls and monitoring to detect unauthorized modifications to referenced repositories, particularly those used in build configuration files. Implementation of these measures aligns with security frameworks that emphasize defense in depth and proper cryptographic key management practices.