CVE-2026-47192
Received Received - Intake

Signature Key Spoofing in kas Setup Tool

Publication date: 2026-08-14

Last updated on: 2026-08-14

Assigner: GitHub, Inc.

Description
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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Meta Information

Published
2026-08-14
Last Modified
2026-08-14
Generated
2026-08-14
AI Q&A
2026-08-14
EPSS Evaluated
N/A
NVD
CVE-2026-47192
EUVD
EUVD-2026-58723

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
siemens kas to 5.3 (exc)
siemens kas 5.3

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-347 The product does not verify, or incorrectly verifies, the cryptographic signature for data.

Attack-Flow Graph

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Executive Summary

CVE-2026-47192 is a Time-of-Check to Time-of-Use (TOCTOU) issue in the Siemens kas tool. It allows attackers to manipulate repositories under specific conditions by replacing a legitimate repository with a malicious one. The vulnerability occurs because kas validates repository signatures after processing configurations, leaving intermediate states vulnerable to tampering.

Detection Guidance

Detecting CVE-2026-47192 requires checking the kas tool version and configuration. Run kas --version to verify if your version is below 5.3. Inspect kas configuration files for repositories referenced by tag without commit IDs and keys stored as files without fingerprints. Check logs for unexpected repository modifications during builds.

Impact Analysis

If exploited, an attacker could replace a repository in your kas configuration with a malicious one. This requires the attacker to control a referenced repository, and you must meet several specific conditions like including a configuration file from their repository without a commit ID or fingerprint. The impact is limited to the vulnerable system itself.

Mitigation Strategies

Upgrade kas to version 5.3 or later immediately. As a temporary workaround, pin signature keys using their fingerprints in your kas configuration. Avoid including configuration files from untrusted repositories and ensure all repository references use commit IDs instead of tags.

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