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Ubuntu 20.04 LTS / 22.04 LTS : pyasn1 vulnerabilities (USN-9011-1)

medium Nessus Plugin ID 378016

Synopsis

The remote Ubuntu host is missing a security update.

Description

The remote Ubuntu 20.04 LTS / 22.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-9011-1 advisory.

 It was discovered that pyasn1 did not properly bound the size of long-form tag identifiers when parsing BER, CER, or DER encoded data. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-59884)

 It was discovered that pyasn1 processed OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-59885)

 It was discovered that pyasn1 incorrectly handled conversion of decoded REAL values to Python float types.
 An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU and memory resources, resulting in a denial of service. This issue only affected Ubuntu 14.04 LTS, Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-59886)

 It was discovered that pyasn1 incorrectly handled tracking component types when decoding containers without a schema. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 26.04 LTS, and Ubuntu 26.10.
 (CVE-2026-119194)

 It was discovered that pyasn1 processed fragmented constructed strings and indefinite-length ANY values in quadratic time. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. This issue was only addressed in Ubuntu 26.04 LTS and Ubuntu 26.10. (CVE-2026-119195)

 It was discovered that pyasn1 processed fragmented constructed BIT STRING values in quadratic time. An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. (CVE-2026-119196)

 It was discovered that pyasn1 processed binary-encoded REAL values with large mantissas in quadratic time.
 An attacker could possibly use this issue to cause applications decoding untrusted ASN.1 data to consume excessive CPU resources, resulting in a denial of service. (CVE-2026-119197)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected pypy-pyasn1, python-pyasn1 and / or python3-pyasn1 packages.

See Also

https://ubuntu.com/security/notices/USN-9011-1

Plugin Details

Severity: Medium

ID: 378016

File Name: ubuntu_USN-9011-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 11/10/2026

Updated: 11/10/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:20.04:-:lts, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:pypy-pyasn1, p-cpe:/a:canonical:ubuntu_linux:python-pyasn1, p-cpe:/a:canonical:ubuntu_linux:python3-pyasn1

Required KB Items: Host/cpu, Host/Debian/dpkg-l, Host/Ubuntu, Host/Ubuntu/release

Exploit Ease: No known exploits are available

Patch Publication Date: 11/9/2026

Vulnerability Publication Date: 11/9/2026

Reference Information

USN: 9011-1