VulnerabilityPublished 14 Jul 2026Updated 9 Nov 2026

CVE-2026-59885: pyasn1 is a generic ASN.1 library for Python

Affects pyasn1Source GCVE Database

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Not known to be exploited · CVSS 7.5 High · fixed in 0.4.8-1ubuntu0.3 : patch pyasn1 soon.

Data as of 10 Nov 2026, 06:10 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 0.4.8-1ubuntu0.3, 0.4.8-4ubuntu0.3, 0.6.3-1ubuntu0.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade the Ubuntu pyasn1 to 0.4.8-1ubuntu0.3 (package) or 0.4.8-4ubuntu0.3 (package) or 0.6.3-1ubuntu0.1 (package).

Patches and advisories

ubuntu.com/security/notices/USN-8712-1 (opens in a new tab)

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSpyasn1`pkg:deb/ubuntu/pyasn1?arch=source&distro=resolute`Other threats	Affected <0.6.3-1ubuntu0.1	Fixed in 0.6.3-1ubuntu0.1
Ubuntu 24.04 LTSpyasn1`pkg:deb/ubuntu/pyasn1?arch=source&distro=noble`Other threats	Affected <0.4.8-4ubuntu0.3	Fixed in 0.4.8-4ubuntu0.3
Ubuntu 22.04 LTSpyasn1`pkg:deb/ubuntu/pyasn1?arch=source&distro=jammy`Other threats	Affected <0.4.8-1ubuntu0.3	Fixed in 0.4.8-1ubuntu0.3
Ubuntu Pro 20.04 LTSpyasn1`pkg:deb/ubuntu/pyasn1?arch=source&distro=esm-infra/focal`Other threats	Affected 0.4.2-3 – 0.4.2-3ubuntu0.20.04.1~esm2 4 affected builds	Fixed in–
Ubuntu Pro 18.04 LTSpyasn1`pkg:deb/ubuntu/pyasn1?arch=source&distro=esm-infra/bionic`Other threats	Affected 0.1.9-2 – 0.4.2-3ubuntu0.18.04.1~esm2 4 affected builds	Fixed in–
Ubuntu Pro 16.04 LTSpyasn1`pkg:deb/ubuntu/pyasn1?arch=source&distro=esm-infra-legacy/xenial`Other threats	Affected 0.1.8-2 – 0.1.9-1ubuntu0.1~esm2 4 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade pyasn1 to version 0.6.4 or later. Ubuntu users should apply security updates that include fixed versions 0.4.8-1ubuntu0.3, 0.4.8-4ubuntu0.3, or 0.6.3-1ubuntu0.1 as referenced in the Ubuntu security notice USN-8712-1. No other mitigation is required as the issue is resolved in these fixed versions.

Description

pyasn1 versions prior to 0.6.4 contain a vulnerability where the BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values with quadratic time complexity relative to the number of arcs. This can cause excessive CPU consumption when decoding crafted payloads with many arcs, leading to denial of service. The encoders exhibit the same behavior when re-encoding attacker-supplied values. The issue is fixed in version 0.6.4.

Impact

An attacker can cause a denial of service by submitting ASN.1 data containing OBJECT IDENTIFIERs with many arcs, which triggers excessive CPU consumption during decoding or encoding. This does not affect confidentiality or integrity but impacts availability of applications using vulnerable pyasn1 versions.

Summary

The pyasn1 library for Python versions before 0.6.4 suffers from a performance vulnerability in its BER, CER, and DER decoders and encoders when handling OBJECT IDENTIFIER and RELATIVE-OID values. The processing time grows quadratically with the number of arcs in the OID, allowing an attacker to craft payloads that cause excessive CPU usage during decode() or re-encode operations. This can result in denial of service conditions in applications that process untrusted ASN.1 data. The vulnerability is addressed in pyasn1 version 0.6.4 and fixed versions listed for Ubuntu packages.

References

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