pyasn1 up to 0.6.3 ASN.1 prettyPrint/str/int/float exponent resource consumption

Summaryinfo

A vulnerability was found in pyasn1 up to 0.6.3. It has been classified as problematic. Impacted is the function prettyPrint/str/int/float of the component ASN.1. The manipulation of the argument exponent leads to resource consumption. This vulnerability is listed as CVE-2026-59886. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in pyasn1 up to 0.6.3 and classified as problematic. This issue affects the function prettyPrint/str/int/float of the component ASN.1. The manipulation of the argument exponent with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-59886 since 07/07/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 0.6.4 eliminates this vulnerability.

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Productinfo

Name

• pyasn1

Version

• 0.6.0
• 0.6.1
• 0.6.2
• 0.6.3

Website

• Product: https://github.com/pyasn1/pyasn1/

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