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.
Fix
Nothing published yet: no patch, vendor advisory or mitigation reference on NVD, no vendor advisory in the News for this CVE, not in CISA's KEV, no fixed package version. BaselineWatch does not guess at one.
Change history 1
- First seenCVSS 7.5 · pyasn1NVD modified 2026-10-29 19:48
Affected (CPE criteria) 0
NVD has not attached CPE configurations yet.
References 4
- https://github.com/pyasn1/pyasn1/security/advisories/GHSA-mm57-4v3p-rchx x_refsource_confirm
- https://github.com/pyasn1/pyasn1/pull/132 x_refsource_misc
- https://github.com/pyasn1/pyasn1/commit/ce3ec3390784780a530047e0e77be5ff457636a4 x_refsource_misc
- https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5 x_refsource_misc