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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References
History
Thu, 29 Oct 2026 22:00:00 +0000
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| 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 | |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-10-29T19:48:52.470Z
Reserved: 2026-10-29T16:04:48.728Z
Link: CVE-2026-119197
No data.
Status : Received
Published: 2026-10-29T20:17:30.907
Modified: 2026-10-29T20:17:30.907
Link: CVE-2026-119197
No data.
OpenCVE Enrichment
Updated: 2026-10-29T21:45:15Z
Weaknesses