CVE-2026-23490

In pyasn1 prior to 0.6.4, the univ.Real type converts its mantissa, base, and exponent to a Python float using exact big-integer exponentiation. A short BER/CER/DER encoded REAL value can carry a very large exponent, causing excessive CPU and memory consumption and application hangs when prettyPrint(), str(), comparison, arithmetic, int(), or explicit float() is called on untrusted ASN.1 data.

The pyasn1 library before version 0.6.4 has a quadratic time complexity in BER, CER, and DER decoders when processing OBJECT IDENTIFIER and RELATIVE-OID values with many arcs. A small crafted payload with many OID arcs causes excessive CPU consumption per decode() call, potentially leading to denial of service in applications processing untrusted ASN.1 data.

The pyasn1 library before version 0.6.4 has a vulnerability in the BER decoder that does not limit the tag ID size when parsing long-form tags, allowing crafted input to force construction of an arbitrarily large integer with quadratic CPU cost and trigger unhandled ValueError exceptions in Python 3.11+.

The pyasn1 library prior to version 0.6.3 is vulnerable to a Denial of Service (DoS) attack due to uncontrolled recursion when decoding deeply nested ASN.1 structures. An attacker can craft a payload with thousands of nested SEQUENCE or SET tags with Indefinite Length markers, causing a stack overflow or memory exhaustion.