pyasn1 up to 0.6.4 Decoder resource consumption

Summaryinfo

A vulnerability, which was classified as problematic, was found in pyasn1 up to 0.6.4. Impacted is the function ConstructedPayloadDecoderBase._decodeComponentsSchemaless of the component Decoder. Executing a manipulation can lead to resource consumption. This vulnerability is tracked as CVE-2026-119194. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in pyasn1 up to 0.6.4. This vulnerability affects the function ConstructedPayloadDecoderBase._decodeComponentsSchemaless of the component Decoder. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-119194 since 10/29/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 0.6.5 eliminates this vulnerability.

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Productinfo

Name

• pyasn1

Version

• 0.6.0
• 0.6.1
• 0.6.2
• 0.6.3
• 0.6.4

Website

• Product: https://github.com/pyasn1/pyasn1/

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