Vulnerability · Published Mar 3, 2026 · Assigned by GitHub_M
CVE-2026-27932joserfc PBES2 p2c Unbounded Iteration Count enables Denial of Service (DoS)
High 7.5
In plain English
A high-severity resource allocation without limits in joserfc from authlib. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | joserfc | no fix listed | DEBIAN-CVE-2026-27932 |
| Debian:14 | joserfc | 1.6.3-1 | DEBIAN-CVE-2026-27932 |
| PyPI | joserfc | 1.6.3 | PYSEC-2026-2529 |
| PyPI | joserfc | 1.6.3 | GHSA-w5r5-m38g-f9f9 |
| Ubuntu:25.10 | joserfc | no fix listed | UBUNTU-CVE-2026-27932 |
| Ubuntu:26.04:LTS | joserfc | no fix listed | UBUNTU-CVE-2026-27932 |
| Ubuntu:26.10 | joserfc | no fix listed | UBUNTU-CVE-2026-27932 |
Affected products (as reported)
Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H