CVE-2026-119195VulnerabilityPublished 31 Oct 2026

Gyb: pyasn1 has quadratic-time denial of service in constructed string and indefinite-length ANY decoding

Affects gybSource GCVE Database

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Authoritative record:CVE-2026-119195· High 7.5

Not known to be exploited · CVSS 7.5 High.

Data as of 31 Oct 2026, 16:20 UTC

CVSS 3.1 base score

7.5High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.5

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 29 Oct 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 30 Oct 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

Affected software

Product	Affected	Fixed in
Homebrewgyb`pkg:brew/gyb`Other threats	Affected >=1.73	Fixed in–

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AI-suggested

Until a fix is available, applications should implement input validation or resource limits to restrict the size and complexity of ASN.1 inputs processed by pyasn1 decoders. Avoid decoding untrusted ASN.1 inputs without such controls. Monitor vendor channels for updates addressing this issue.

Description

pyasn1 versions 0.6.4 and earlier contain a denial-of-service vulnerability due to quadratic-time complexity in decoding constructed OCTET STRINGs, character strings, and indefinite-length ANY types. This occurs when decoding many fixed-size fragments, causing excessive CPU usage. The issue affects BER and CER decoding and certain non-conforming DER inputs. An attacker supplying crafted ASN.1 input to an affected decoder can cause CPU exhaustion. No confidentiality or integrity impact is reported.

Impact

An attacker who can supply crafted ASN.1 input to an application using pyasn1 0.6.4 or earlier can cause the decoder to consume disproportionate CPU resources, leading to denial of service through CPU exhaustion. This affects applications that decode BER or CER encoded constructed strings or indefinite-length ANY types without adequate input or resource limits. There is no impact on confidentiality or integrity. The CVSS v3.1 base score is 7.5 (high severity) reflecting network attack vector, low complexity, no privileges required, no user interaction, and impact on availability only.

Summary

In pyasn1 version 0.6.4 and earlier, the BER and CER decoders for constructed OCTET STRINGs, constructed character strings, and indefinite-length ANY types use string reassembly loops that concatenate fragments inefficiently, resulting in O(N²) CPU time relative to the number of fragments. This occurs because each fragment is appended to a growing bytes object, causing repeated copying of the accumulated data. The DER decoder rejects constructed OCTET STRINGs generally but accepts certain non-DER constructed strings when an asn1Spec is provided, exposing the same issue. The vulnerability allows an attacker to supply ASN.1 input that causes excessive CPU consumption during decoding, potentially leading to denial of service. The problem is distinct from a previously fixed OID-related issue and affects multiple ASN.1 string types inheriting the same decoder path.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 16:20 UTC

Technical details

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