CVE-2026-27932
HIGH
GHSA-w5r5-m38g-f9f9
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4Description
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In 1.6.2 and earlier, a resource exhaustion vulnerability in joserfc allows an unauthenticated attacker to cause a Denial of Service (DoS) via CPU exhaustion. When the library decrypts a JSON Web Encryption (JWE) token using Password-Based Encryption (PBES2) algorithms, it reads the p2c (PBES2 Count) parameter directly from the token's protected header. This parameter defines the number of iterations for the PBKDF2 key derivation function. Because joserfc does not validate or bound this value, an attacker can specify an extremely large iteration count (e.g., 2^31 - 1), forcing the server to expend massive CPU resources processing a single token. This vulnerability exists at the JWA layer and impacts all high-level JWE and JWT decryption interfaces if PBES2 algorithms are allowed by the application's policy.
Analysis
Joserfc versions 1.6.2 and earlier fail to validate the PBES2 iteration count parameter in JWE tokens, allowing unauthenticated attackers to trigger CPU exhaustion by specifying arbitrarily large values in the p2c header field. An attacker can exploit this resource exhaustion vulnerability to cause denial of service against any system using the library to decrypt JWE tokens. …
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Remediation
Within 24 hours: Identify all systems and applications using joserfc library and document their criticality and internet exposure. Within 7 days: Apply available vendor patch to all affected systems, prioritizing internet-facing and production environments. …
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