Ubuntu addresses multiple pyasn1 vulnerabilities causing denial of service

Ubuntu has released security updates to address a series of vulnerabilities within the pyasn1 Python library. These flaws primarily involve improper handling of various ASN.1 encoding formats, including BER, CER, and DER. An attacker providing untrusted data could exploit these issues to cause significant resource exhaustion.

The vulnerabilities lead to denial of service (DoS) conditions through excessive CPU and memory usage. The affected Ubuntu releases range from legacy versions like 14.04 LTS up to the latest 26.10 interim release, depending on the specific CVE involved. Users on older LTS distributions should verify their package versions to ensure protection against these resource exhaustion vectors.

Technical breakdown of pyasn1 vulnerabilities

• Tag Identifier Bounds: CVE-2026-59884 involves a failure to properly bound the size of long-form tag identifiers during parsing, leading to CPU exhaustion.
• Algorithmic Complexity: Multiple CVEs (CVE-2026-59885, CVE-2026-119195, CVE-2026-119196, and CVE-2026-119197) involve quadratic time processing for OBJECT IDENTIFIER arcs, fragmented constructed strings, BIT STRING values, and binary-encoded REAL values with large mantissas.
• Type Conversion and Tracking: CVE-2026-59886 involves incorrect conversion of decoded REAL values to Python floats, while CVE-2026-119194 relates to improper component type tracking when decoding containers without a schema.
• Resource Exhaustion: All identified vulnerabilities are categorized as potential denial of service attacks due to the disproportionate consumption of CPU and memory resources.

Why it matters

Since pyasn1 is a fundamental library for handling ASN.1 encoded data, these vulnerabilities impact any Python-based application performing cryptographic or network protocol parsing. System administrators managing long-term support (LTS) environments must prioritize these updates to prevent service disruptions caused by malformed network packets or files.