pyasn1 has quadratic-complexity denial of service in binary REAL decoding

[ Description ]Official 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.

[ Fixes ]Fixes and patches

• pyasn1 0.6.5Fixed version · GitHub Advisories · pip package pyasn1: upgrade to 0.6.5 or later (affected <= 0.6.4)

[ Packages ]Affected open-source packages

• pyasn1 pipAffected <= 0.6.4 · fixed in 0.6.5 · GHSA-mm57-4v3p-rchx

[ References ]References

• github.com/pyasn1/pyasn1/commit/ce3ec3390784780a530047e0e77be5ff457636a4
• github.com/pyasn1/pyasn1/pull/132
• github.com/pyasn1/pyasn1/releases/tag/v0.6.5
• github.com/pyasn1/pyasn1/security/advisories/GHSA-mm57-4v3p-rchx