pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, binary REAL decoding builds a large mantissa one octet at a time by shifting a growing integer and slicing the remaining byte string. Attacker-controlled ASN.1 includes a binary-encoded REAL with a large mantissa and reaches BER, CER, or DER decode(), with or without a schema containing REAL. RealPayloadDecoder.valueDecoder repeatedly performs a left shift, OR, and suffix copy for every mantissa octet, making decode time quadratic in mantissa length. A comparatively small REAL value can hold a decoding worker on one CPU core for seconds or longer and cause availability loss. This issue is fixed in version 0.6.5.
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Fixes

Solution

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Workaround

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History

Fri, 30 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 29 Oct 2026 22:00:00 +0000

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

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

Type Values Removed Values Added
Description pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, binary REAL decoding builds a large mantissa one octet at a time by shifting a growing integer and slicing the remaining byte string. Attacker-controlled ASN.1 includes a binary-encoded REAL with a large mantissa and reaches BER, CER, or DER decode(), with or without a schema containing REAL. RealPayloadDecoder.valueDecoder repeatedly performs a left shift, OR, and suffix copy for every mantissa octet, making decode time quadratic in mantissa length. A comparatively small REAL value can hold a decoding worker on one CPU core for seconds or longer and cause availability loss. This issue is fixed in version 0.6.5.
Title pyasn1: Quadratic-complexity denial of service in binary REAL 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'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-30T16:08:50.120Z

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

Link: CVE-2026-119197

cve-icon Vulnrichment

Updated: 2026-10-30T15:47:15.895Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-29T20:17:30.907

Modified: 2026-10-30T17:18:03.880

Link: CVE-2026-119197

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-29T21:45:15Z

Weaknesses