Executive brief
A security flaw has been identified in m2crypto, a library used by various software applications to handle encrypted communications. This vulnerability could allow a remote attacker to decrypt sensitive data sent over the network by exploiting a timing-based weakness in how the system handles certain encryption keys. If exploited, confidential information such as login credentials or private messages could be exposed to unauthorized parties.
Technical details
m2crypto is vulnerable to a Bleichenbacher-style timing attack (Marvin Attack) due to an incomplete fix for CVE-2020-25657. The vulnerability exists in the RSA decryption API when PKCS#1 v1.5 padding is used, where observable discrepancies in processing time (CWE-203) allow an attacker to perform side-channel analysis. A remote, unauthenticated attacker can capture TLS traffic and iteratively query the server to eventually decrypt the ciphertext. Because the issue is rooted in the API design, a full fix within the library is difficult; mitigation involves using a cryptographic backend that implements implicit rejection or avoiding RSA key exchanges in favor of modern alternatives like ECDHE.
Affected products
- m2crypto project m2crypto -
- Red Hat Enterprise Linux 8.0
- Red Hat Enterprise Linux 9.0
- Red Hat Update Infrastructure 4
- Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem All versions
Timeline
- 2023-12-13: disclosed: Bug reported to Red Hat Bugzilla
- 2024-02-05: advisory: NVD publication date
- 2024-04-09: advisory: Siemens advisory published including this CVE