libjwt 1.15.3 uses strcmp (which is not constant time) to verify authentication, which makes it easier to bypass authentication via a timing side channel.
The strcmp function terminates string comparison upon encountering the first difference, causing the operation execution time to depend on the number of matching characters at the beginning of the compared values. An attacker can measure server response time for successive authentication attempts to gradually guess the correct JWT token value character by character. This type of attack, known as timing side channel, allows effective bypass of the verification mechanism even without knowledge of the secret signing the token.
An unauthenticated remote attacker can bypass JWT-based authentication mechanism and gain unauthorized access to protected application resources, potentially leading to breach of confidentiality, integrity, and availability of data.
Apply patches available from the vendor according to references. Debian Linux users should install the update described in the debian-lts-announce message from February 2024.
libjwt version 1.15.3 and libjwt packages available in Debian Linux (covered by Debian LTS announcement)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HDebian
OSDebian10.0Libjwt
APPLibjwt1.15.3
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