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CVE-2026-48990— joserfc: b64=false RFC7797 JWS payloads bypass JWSRegistry payload-size limits during deserialization

Quick assessment

Affected
authlib joserfc
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Authlib joserfc是Authlib组织开源的一个 Python 库，全面实现了 JOSE（JSON Object Signing and Encryption）系列标准，包括 JWS、JWE、JWK、JWT 等 RFC 规范，用于安全地处理 JSON 数据的签名与加密。 Authlib joserfc 1.3.4版本至1.6.5版本存在安全漏洞，该漏洞源于未对RFC7797 b64=false JWS有效载荷应用JWSRegistry.max_payload_length限制，可能导致资源耗尽

CVSS 5.3 · Medium EPSS 0.16% · P6

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
authlib joserfc < 1.6.7 affected
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I. Basic Information for CVE-2026-48990

Vulnerability Information
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Vulnerability Title
joserfc: b64=false RFC7797 JWS payloads bypass JWSRegistry payload-size limits during deserialization
Source: CVE Program / CVE List V5
Vulnerability Description
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. In versions 1.3.4 through 1.6.5, joserfc accepts oversized RFC7797 b64=false JWS payloads without applying JWSRegistry.max_payload_length, which can lead to resource exhaustion. The normal JWS compact and flattened JSON paths reject payloads above the configured payload-size limit with ExceededSizeError. The RFC7797 unencoded payload paths do not make the same check. A valid b64=false compact or flattened JSON JWS can therefore deserialize successfully with a payload larger than JWSRegistry.max_payload_length. Applications that accept lower-trust JWS values and rely on joserfc to reject oversized token content during verification have a moderate availability risk. This issue has been fixed in version 1.6.7.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
Authlib joserfc 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Authlib joserfc是Authlib组织开源的一个 Python 库，全面实现了 JOSE（JSON Object Signing and Encryption）系列标准，包括 JWS、JWE、JWK、JWT 等 RFC 规范，用于安全地处理 JSON 数据的签名与加密。 Authlib joserfc 1.3.4版本至1.6.5版本存在安全漏洞，该漏洞源于未对RFC7797 b64=false JWS有效载荷应用JWSRegistry.max_payload_length限制，可能导致资源耗尽
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
authlib joserfc < 1.6.7 -

II. Public POCs for CVE-2026-48990

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III. Intelligence Information for CVE-2026-48990

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Patches & Fixes for CVE-2026-48990 (1)

Vendor Advisories for CVE-2026-48990 (1)

IV. Related Vulnerabilities

Same product: joserfc
Same vendor: authlib
Same weakness: CWE-400

V. Comments for CVE-2026-48990

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