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.
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-w5r5-m38g-f9f9 joserfc's PBES2 p2c Unbounded Iteration Count enables Denial of Service (DoS)
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 04 Mar 2026 22:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 04 Mar 2026 15:00:00 +0000

Type Values Removed Values Added
First Time appeared Authlib
Authlib joserfc
Vendors & Products Authlib
Authlib joserfc

Tue, 03 Mar 2026 23:00:00 +0000

Type Values Removed Values Added
Description 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.
Title joserfc PBES2 p2c Unbounded Iteration Count enables Denial of Service (DoS)
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-03-04T21:20:55.097Z

Reserved: 2026-02-25T03:11:36.688Z

Link: CVE-2026-27932

cve-icon Vulnrichment

Updated: 2026-03-04T21:20:50.283Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-03-03T23:15:56.050

Modified: 2026-03-04T18:08:05.730

Link: CVE-2026-27932

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-03-04T14:53:29Z

Weaknesses