VulnerabilityPublished 31 Oct 2026

CVE-2026-119196: Oterm · pyasn1 has quadratic CPU consumption in constructed BIT STRING decoding

Affects otermSource GCVE Database

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Authoritative record:CVE-2026-119196· High 7.5

Not known to be exploited · CVSS 7.5 High.

Data as of 31 Oct 2026, 17:06 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
Homebrewoterm`pkg:brew/oterm`Other threats	Affected >=0.15.0	Fixed in–

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AI-suggested

Until a fix is available, applications should consider restricting or validating ASN.1 input sizes and fragment counts to limit exposure to this CPU exhaustion vulnerability. Avoid automatic decoding of untrusted ASN.1 data without input validation.

Description

CVE-2026-119196 is a denial-of-service vulnerability in the pyasn1 library (up to version 0.6.4) affecting the decoding of constructed BIT STRING values. The vulnerable code path causes quadratic CPU consumption when decoding ASN.1 data with many fragments, potentially exhausting CPU resources during decoding. This affects BER and CER decoders and certain schema-driven DER decoding paths. The vulnerability does not impact confidentiality or integrity but may cause denial of service by occupying decoding threads.

Impact

An attacker who can supply sufficiently large, crafted ASN.1 inputs to an application using the affected pyasn1 decoders may cause CPU exhaustion during decoding, leading to denial of service. The vulnerability does not affect confidentiality or integrity. The impact depends on whether the application accepts untrusted ASN.1 data and the input size limits enforced. The CVSS v3.1 base score is 7.5 (high) assuming network-exposed unauthenticated input and automatic decoding.

Summary

In pyasn1 versions through 0.6.4, decoding constructed BIT STRING values with many fragments leads to quadratic CPU time due to repeated shifting and copying of the accumulated value in the BitStringPayloadDecoder. Both definite-length and indefinite-length fragment loops invoke a method that shifts an increasingly large integer for each fragment, resulting in O(n²) complexity for n fragments. This affects BER and CER decoders and schema-driven DER decoding that accepts definite-length constructed BIT STRINGs, despite constructed BIT STRING not being valid DER. The vulnerability allows an attacker to cause CPU exhaustion by supplying large crafted ASN.1 inputs to affected decoders, potentially causing denial of service in applications that automatically decode untrusted ASN.1 data.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 17:06 UTC

Technical details

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