CVE-2026-59885

A flaw was found in pyasn1, a Python library for Abstract Syntax Notation One (ASN.1). The BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. A remote attacker could exploit this by providing a specially crafted payload containing an OID with many arcs, leading to excessive CPU consumption and a denial of service (DoS) in applications that decode untrusted ASN.1 data. The corresponding encoders also exhibit this quadratic behavior when re-encoding attacker-supplied values.

A flaw was found in pyasn1. The BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. A small crafted payload containing an OID with many arcs consumes excessive CPU per decode() call, allowing denial of service in applications that decode untrusted ASN.1 data (certificates, LDAP, SNMP, Kerberos). The corresponding encoders exhibit the same behavior when re-encoding attacker-supplied values. The arc-size limit introduced for CVE-2026-23490 does not mitigate this issue. This issue is fixed in pyasn1 version 0.6.4.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Update to pyasn1 version 0.6.4 or later when available for your product stream. The impact is limited to availability (denial of service) — an attacker cannot access or modify data. Applications that do not process untrusted ASN.1 input are at reduced risk.