Joserfc
CVE-2025-65015
CRITICAL
GHSA-frfh-8v73-gjg4
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V2 - Validation and Business Logic Resource allocation limits
MITRE ATT&CK
1 technique across 1 tactic: Impact The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 9.2 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available. EPSS exploitation probability: 0.07%. |
| Exploit ScenarioDerived | A remote attacker could exhaust system resources through uncontrolled allocation by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
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Alert meAnalysisAIv1 – Mar 28, 2026
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Rated critical severity (CVSS 9.2), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Set resource limits, implement rate limiting, validate input sizes.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in pypi
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Allocation of Resources Without Limits (CWE-770), which allows attackers to exhaust system resources through uncontrolled allocation. joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In versions from 1.3.3 to before 1.3.5 and from 1.4.0 to before 1.4.2, the ExceededSizeError exception messages are embedded with non-decoded JWT token parts and may cause Python logging to record an arbitrarily large, forged JWT payload. In situations where a misconfigured - or entirely absent - production-grade web server sits in front of a Python web application, an attacker may be able to send arbitrarily large bearer tokens in the HTTP request headers. When this occurs, Python logging or diagnostic tools (e.g., Sentry) may end up processing extremely large log messages containing the full JWT header during the joserfc.jwt.decode() operation. The same behavior also appears when validating claims and signature payload sizes, as the library raises joserfc.errors.ExceededSizeError() with the full payload embedded in the exception message. Since the payload is already fully loaded into memory at this stage, the library cannot prevent or reject it. This issue has been patched in versions 1.3.5 and 1.4.2. Affected products include: Hsiaoming Joserfc. Version information: before 1.3.5.
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Severity by source
Sources disagree (Medium–Critical)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.
CVSS VectorVendor: github
Lifecycle Timeline
3DescriptionCVE.org
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In versions from 1.3.3 to before 1.3.5 and from 1.4.0 to before 1.4.2, the ExceededSizeError exception messages are embedded with non-decoded JWT token parts and may cause Python logging to record an arbitrarily large, forged JWT payload. In situations where a misconfigured - or entirely absent - production-grade web server sits in front of a Python web application, an attacker may be able to send arbitrarily large bearer tokens in the HTTP request headers. When this occurs, Python logging or diagnostic tools (e.g., Sentry) may end up processing extremely large log messages containing the full JWT header during the joserfc.jwt.decode() operation. The same behavior also appears when validating claims and signature payload sizes, as the library raises joserfc.errors.ExceededSizeError() with the full payload embedded in the exception message. Since the payload is already fully loaded into memory at this stage, the library cannot prevent or reject it. This issue has been patched in versions 1.3.5 and 1.4.2.
Executive ViewAI
Organizations using versions from 1.3.3 to face critical risk from CVE-2025-65015 rated CVSS 9.2. Successful exploitation could critically impact the confidentiality, integrity, and availability of affected systems. Proof-of-concept code is publicly available, increasing the risk of exploitation. A patch is available and should be applied immediately given the critical severity.
Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
Affected Products (CPE)CVE.org
Joserfc versions 1.6.2 and earlier fail to validate the PBES2 iteration count parameter in JWE tokens, allowing unauthen
Memory exhaustion in joserfc before 1.7.6 allows remote unauthenticated attackers to force a roughly token-sized extra a
Resource exhaustion in joserfc (versions 1.3.4-1.6.5) is possible because the RFC7797 unencoded-payload (b64=false) JWS
Authentication bypass in the joserfc Python library before 1.7.4 lets remote, unauthenticated attackers submit a JWS Gen
CPU-exhaustion denial of service in joserfc prior to 1.7.5 affects any Python service that passes externally supplied JW
JWT malleability in joserfc versions 1.7.1 and prior allows a low-privileged user holding a valid token to craft alterna
Exploit-DB