CVE-2025-53013: Auth Bypass (CVSS 5.2)

Description

Himmelblau is an interoperability suite for Microsoft Azure Entra ID and Intune. A vulnerability present in versions 0.9.10 through 0.9.16 allows a user to authenticate to a Linux host via Himmelblau using an *invalid* Linux Hello PIN, provided the host is offline. While the user gains access to the local system, Single Sign-On (SSO) fails due to the network being down and the inability to issue tokens (due to a failure to unlock the Hello key). The core issue lies in an incorrect assumption within the `acquire_token_by_hello_for_business_key` function: it was expected to return a `TPMFail` error for an invalid Hello key when offline, but instead, a preceding nonce request resulted in a `RequestFailed` error, leading the system to erroneously transition to an offline success state without validating the Hello key unlock. This impacts systems using Himmelblau for authentication when operating in an offline state with Hello PIN authentication enabled. Rocky Linux 8 (and variants) are not affected by this vulnerability. The problem is resolved in Himmelblau version 0.9.17. A workaround is available for users who cannot immediately upgrade. Disabling Hello PIN authentication by setting `enable_hello = false` in `/etc/himmelblau/himmelblau.conf` will mitigate the vulnerability.

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CVSS v3.1 Score

5.2

MEDIUM

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Weakness Type (CWE)

CWE-287 Improper Authentication

References

Other References

https://github.com/himmelblau-idm/himmelblau/commit/64b03739f1d5ee472b1cff3ed20ed9af1c65a6f8 https://github.com/himmelblau-idm/himmelblau/commit/78477d684df710d57c10091c87b92665cfac98ae https://github.com/himmelblau-idm/himmelblau/security/advisories/GHSA-j93j-pwm6-p97j https://www.vicarius.io/vsociety/posts/cve-2025-53013-detect-himmelblau-vulnerable-configuration https://www.vicarius.io/vsociety/posts/cve-2025-53013-mitigate-himmelblau-vulnerable-configuration

Frequently Asked Questions

What is CVE-2025-53013? +

Himmelblau is an interoperability suite for Microsoft Azure Entra ID and Intune. A vulnerability present in versions 0.9.10 through 0.9.16 allows a user to authenticate to a Linux host via Himmelblau using an *invalid* Linux Hello PIN, provided the host is offline. While the user gains access to the local system, Single Sign-On (SSO) fails due to the network being down and the inability to issue tokens (due to a failure to unlock the Hello key). The core issue lies in an incorrect assumption within the `acquire_token_by_hello_for_business_key` function: it was expected to return a `TPMFail` error for an invalid Hello key when offline, but instead, a preceding nonce request resulted in a `RequestFailed` error, leading the system to erroneously transition to an offline success state without validating the Hello key unlock. This impacts systems using Himmelblau for authentication when operating in an offline state with Hello PIN authentication enabled. Rocky Linux 8 (and variants) are not affected by this vulnerability. The problem is resolved in Himmelblau version 0.9.17. A workaround is available for users who cannot immediately upgrade. Disabling Hello PIN authentication by setting `enable_hello = false` in `/etc/himmelblau/himmelblau.conf` will mitigate the vulnerability. It has a CVSS v3.1 base score of 5.2 (MEDIUM).

How severe is CVE-2025-53013? +

CVE-2025-53013 has a CVSS v3.1 score of 5.2 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2025-53013? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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