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CVE-2026-119194— pyasn1: Quadratic CPU use in schemaless BER/CER/DER container decoding

Quick assessment

Affected

pyasn1 pyasn1

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.

pyasn1 是一个面向 Python 的通用 ASN.1 库。在 0.3.3 至 0.6.5 版本中，无模式（schemaless）容器解码会将每个已解码组件的 TagSet 存储到一个持续增长的集合中，尽管实际上只需区分“单一标签”与“多个标签”这两种类型。攻击者可构造包含大量不同长标签 ID 的 BER、CER 或 DER 输入，使这些标签的 TagSet 哈希发生碰撞。在中，每次后续插入操作都需要与数量不断增长的先前碰撞标签进行比较，从而导致 CPU 工作量呈二次方增长，而解码后的值及其顺序仍然保持有效。

CVSS 7.5 · High Updated Oct 30, 2026

Possible ATT&CK Techniques 1 AI

T1499.003 · Application Exhaustion Flood

Affected Version Matrix 1

Vendor	Product	Version Range	Status
pyasn1	pyasn1	`>= 0.3.3, < 0.6.5`	affected

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Vulnerability Information

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Vulnerability Title

pyasn1: Quadratic CPU use in schemaless BER/CER/DER container decoding

Source: CVE Program / CVE List V5

Vulnerability Description

pyasn1 is a generic ASN.1 library for Python. From 0.3.3 until 0.6.5, schemaless container decoding stores every decoded component's TagSet in a growing set even though only one-versus-multiple tag types must be distinguished. Attacker-controlled BER, CER, or DER input contains many distinct long tag IDs whose TagSet hashes collide. Each later set insertion compares against an increasing number of earlier colliding tags in ConstructedPayloadDecoderBase._decodeComponentsSchemaless, producing quadratic CPU work while decoded values and order remain valid. Repeated inputs can exhaust decoder CPU and reduce service availability. This issue is fixed in version 0.6.5.

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

算法复杂性

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
pyasn1	pyasn1	>= 0.3.3, < 0.6.5	-

II. Public POCs for CVE-2026-119194

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-119194

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Other References for CVE-2026-119194 (4)

https://github.com/pyasn1/pyasn1/pull/132 x_refsource_MISC
https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5 x_refsource_MISC
https://github.com/pyasn1/pyasn1/security/advisories/GHSA-fm9c-5rcf-2q5p x_refsource_CONFIRM
https://github.com/pyasn1/pyasn1/commit/a36e3a3d067148d26197a6b7221fd0e2cde9cc86 x_refsource_MISC

https://www.cve.org/CVERecord?id=CVE-2026-119194

Same Patch Batch · pyasn1 · 2026-10-29 · 4 CVEs total

CVE-2026-119197	7.5 HIGH	pyasn1: Quadratic-complexity denial of service in binary REAL decoding
CVE-2026-119196	7.5 HIGH	pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding
CVE-2026-119195	7.5 HIGH	pyasn1: Quadratic-time denial of service in constructed string and indefinite-length ANY d

IV. Related Vulnerabilities

Same product: pyasn1

Same vendor: pyasn1

Same weakness: CWE-407