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CVE-2026-119196— pyasn1: Quadratic CPU consumption in constructed BIT STRING 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 是一个用于 Python 的通用 ASN.1 库。在 0.6.5 版本之前，构造型位串（BIT STRING）的解码过程会反复对从先前片段累积的完整位值进行移位和复制。如果攻击者控制的 BER 或 CER 输入包含大量构造型位串片段，或者由模式驱动的 DER 接受定长构造型位串，则 BitStringPayloadDecoder 会反复调用 BitString.fromOctetString，并将先前的位串作为前缀追加，导致每个片段处理时都需要对不断增大的 SizedInteger 进行移位操作，从而

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	`< 0.6.5`	affected

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Vulnerability Information

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Vulnerability Title

pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding

Source: CVE Program / CVE List V5

Vulnerability Description

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed BIT STRING decoding repeatedly shifts and copies the complete bit value accumulated from earlier fragments. Attacker-controlled BER or CER input contains many constructed BIT STRING fragments; schema-driven DER also accepts a definite-length constructed BIT STRING. BitStringPayloadDecoder repeatedly calls BitString.fromOctetString with the prior bitString as prepend, shifting an ever-growing SizedInteger for each fragment and causing quadratic work. Large fragmented values can exhaust CPU during decode() without requiring later conversion or formatting. 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	< 0.6.5	-

II. Public POCs for CVE-2026-119196

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-119196

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Other References for CVE-2026-119196 (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-2qm8-x737-gmw5 x_refsource_CONFIRM
https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c x_refsource_MISC

https://www.cve.org/CVERecord?id=CVE-2026-119196

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-2026-119194	7.5 HIGH	pyasn1: Quadratic CPU use in schemaless BER/CER/DER container 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