USN-9011-1: pyasn1 vulnerabilities

Publication date

9 November 2026

Overview

Several security issues were fixed in pyasn1.


Packages

  • pyasn1 - ASN.1 library for Python

Details

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...

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)


Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

The problem can be corrected by updating your system to the following package versions:

Ubuntu Release Package Version
26.10 stonking python3-pyasn1 –  0.6.4-1ubuntu0.1
26.04 LTS resolute python3-pyasn1 –  0.6.3-1ubuntu0.2
24.04 LTS noble python3-pyasn1 –  0.4.8-4ubuntu0.4
22.04 LTS jammy python3-pyasn1 –  0.4.8-1ubuntu0.4
20.04 LTS focal pypy-pyasn1 –  0.4.2-3ubuntu0.20.04.1~esm2  
python-pyasn1 –  0.4.2-3ubuntu0.20.04.1~esm2  
python3-pyasn1 –  0.4.2-3ubuntu0.20.04.1~esm2  
18.04 LTS bionic pypy-pyasn1 –  0.4.2-3ubuntu0.18.04.1~esm2  
python-pyasn1 –  0.4.2-3ubuntu0.18.04.1~esm2  
python3-pyasn1 –  0.4.2-3ubuntu0.18.04.1~esm2  
16.04 LTS xenial pypy-pyasn1 –  0.1.9-1ubuntu0.1~esm2  
python-pyasn1 –  0.1.9-1ubuntu0.1~esm2  
python3-pyasn1 –  0.1.9-1ubuntu0.1~esm2  
14.04 LTS trusty python-pyasn1 –  0.1.7-1ubuntu2.1+esm2  
python3-pyasn1 –  0.1.7-1ubuntu2.1+esm2  

Reduce your security exposure

Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines.


Have additional questions?

Talk to a member of the team ›