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.

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Thu, 29 Oct 2026 20:45:00 +0000

Type Values Removed Values Added
First Time appeared Pyasn1
Pyasn1 pyasn1
Vendors & Products Pyasn1
Pyasn1 pyasn1

Thu, 29 Oct 2026 19:45:00 +0000

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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.
Title pyasn1: Quadratic CPU use in schemaless BER/CER/DER container decoding
Weaknesses CWE-407
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-29T19:38:14.056Z

Reserved: 2026-10-29T16:04:48.728Z

Link: CVE-2026-119194

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-29T20:17:30.480

Modified: 2026-10-29T20:17:30.480

Link: CVE-2026-119194

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-29T20:45:14Z

Weaknesses