CVE-2025-49506 in Portable Runtime Utility
Summary
by MITRE • 08/06/2026
APR-util versions 1.6.3 (and earlier) function apr_password_validate() was not constant-time with regards to hashes or passwords comparisons, potentially leaking their content via a side channel timing attack particularly on platforms without crypt() such as Windows, BeOS, NetWare, or Android.
Users are recommended to upgrade to version 1.6.4, which fixes this issue.
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Analysis
by VulDB Data Team • 08/06/2026
The apr-util library vulnerability stems from a critical timing side-channel weakness in the apr_password_validate() function affecting versions 1.6.3 and earlier. This flaw represents a classic implementation of constant-time comparison failures that directly violates fundamental security principles for cryptographic operations. The vulnerability specifically impacts platforms lacking robust crypt() implementations including Windows, BeOS, NetWare, and Android systems where the library falls back to non-constant time comparison methods.
The technical nature of this vulnerability manifests through timing variations that occur during password hash validation processes. When comparing passwords or hashes using non-constant time algorithms, attackers can measure microsecond differences in execution time to infer information about the target values. This timing leakage creates a covert channel through which sensitive data can be gradually reconstructed without direct access to the underlying cryptographic materials. The vulnerability maps directly to CWE-208, which specifically addresses timing side channels in cryptographic implementations.
The operational impact of this vulnerability extends beyond simple credential theft, as it enables sophisticated attackers to perform systematic timing analysis attacks against authentication systems relying on apr-util. On platforms without proper crypt() support, the library's fallback mechanisms introduce predictable timing variations that can be exploited through repeated authentication attempts or by observing response times during validation processes. This weakness particularly affects web applications, database authentication systems, and any service utilizing the apr-util library for password handling functions.
Security practitioners should note this vulnerability aligns with ATT&CK technique T1212, which covers exploitation of credential exposure through timing attacks against cryptographic implementations. The risk is particularly elevated in environments where attackers can repeatedly attempt authentication or monitor system responses over time. Organizations using affected versions face potential credential compromise and unauthorized access to protected systems.
The recommended mitigation involves immediate upgrading to apr-util version 1.6.4, which implements proper constant-time comparison algorithms throughout the password validation process. This fix ensures that hash and password comparisons execute in consistent time regardless of input values, eliminating the timing side-channel that previously enabled information leakage. System administrators should prioritize this upgrade across all affected platforms and verify that the updated library properly handles authentication scenarios without introducing regressions in functionality or performance characteristics.