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CVE-2026-59884— pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs

Quick assessment

Affected
pyasn1 pyasn1
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

pyasn1是pyasn1组织开源的一个PythonASN.1库。 pyasn1 0.6.4之前版本存在资源管理错误漏洞，该漏洞源于BER解码器在解析长格式标签时无限制累积连续八位组，可能允许通过特制输入强制构建任意大整数，导致CPU成本二次增长并触发Python 3.11+错误格式化路径中未处理的ValueError异常。

CVSS 7.5 · High EPSS 0.62% · P49

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
pyasn1 pyasn1 < 0.6.4 affected
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I. Basic Information for CVE-2026-59884

Vulnerability Information
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Vulnerability Title
pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs
Source: CVE Program / CVE List V5
Vulnerability Description
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.
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:H
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
pyasn1 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
pyasn1是pyasn1组织开源的一个PythonASN.1库。 pyasn1 0.6.4之前版本存在资源管理错误漏洞，该漏洞源于BER解码器在解析长格式标签时无限制累积连续八位组，可能允许通过特制输入强制构建任意大整数，导致CPU成本二次增长并触发Python 3.11+错误格式化路径中未处理的ValueError异常。
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
pyasn1 pyasn1 < 0.6.4 -

II. Public POCs for CVE-2026-59884

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
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claude_code · 10748 chars
GitHub 复现环境（可 clone 直接跑）
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III. Intelligence Information for CVE-2026-59884

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Patches & Fixes for CVE-2026-59884 (1)

Vendor Advisories for CVE-2026-59884 (1)

Vendor Pages for CVE-2026-59884 (1)

Same Patch Batch · pyasn1 · 2026-07-14 · 3 CVEs total

CVE-2026-59886 7.5 HIGH pyasn1: Uncontrolled resource consumption when converting decoded REAL values
CVE-2026-59885 7.5 HIGH pyasn1: Quadratic complexity in OBJECT IDENTIFIER and RELATIVE-OID processing allows denia

IV. Related Vulnerabilities

Same product: pyasn1
Same vendor: pyasn1
Same weakness: CWE-400