pyasn1 up to 0.6.4 Bit String Decoding BitString.fromOctetString resource consumption

Summaryinfo

A vulnerability was found in pyasn1 up to 0.6.4 and classified as problematic. The impacted element is the function BitString.fromOctetString of the component Bit String Decoding. The manipulation results in resource consumption. This vulnerability is cataloged as CVE-2026-119196. The attack may be launched remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in pyasn1 up to 0.6.4. Affected is the function BitString.fromOctetString of the component Bit String Decoding. The manipulation with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as 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. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-119196 since 10/29/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1499 by the MITRE ATT&CK project.

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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