High [CVE-2026-59886] Denial of Service via crafted ASN.1 REAL values

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the univ.

Real type converted its mantissa, base, and exponent value to a Python float using exact big-integer exponentiation.

A BER, CER, or DER encoded REAL value only a few bytes long can carry a very large exponent, causing float conversion through prettyPrint(), str(), comparison, arithmetic, int(), or an explicit float() call to consume excessive CPU and memory and hang applications that decode untrusted ASN.1 data and then print, log, or compare decoded objects.

This issue is fixed in version 0.6.4. When the application subsequently prints, logs, compares, or performs arithmetic on the decoded value, this can cause excessive CPU and memory consumption, leading to a denial of service (DoS).

This flaw in pyasn1, rated as Important, could lead to a denial of service in Red Hat products that process untrusted ASN.1 data.

A remote attacker could send a specially crafted BER, CER, or DER encoded REAL value with a large exponent, causing applications to consume excessive resources during decoding operations such as printing, logging, or arithmetic, thereby rendering the service unavailable. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Weakness: CWE-770.