VulnerabilityPublished 31 Oct 2026

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

Affects parsedmarcSource 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, 16:05 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
Homebrewparsedmarc`pkg:brew/parsedmarc`Other threats	Affected >=8.11.0	Fixed in–

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AI-suggested

Until a fix is available, applications should implement input validation or limits to restrict the size and complexity of ASN.1 constructed BIT STRING inputs to prevent CPU exhaustion. Avoid decoding untrusted ASN.1 data without such controls. Monitor vendor communications for updates and patches addressing this vulnerability.

Description

CVE-2026-119196 is a denial-of-service vulnerability in pyasn1 through version 0.6.4, where decoding constructed BIT STRING values with many fragments causes quadratic CPU consumption. This occurs because the decoder repeatedly shifts and copies the accumulated value for each fragment, leading to CPU exhaustion during decode(). The vulnerability affects BER and CER decoders and certain schema-driven DER decoding paths. No confidentiality or integrity impact is reported. The issue can be triggered by attacker-controlled ASN.1 input if the application accepts such input without sufficient limits.

Impact

An attacker can cause denial of service by supplying crafted ASN.1 data containing constructed BIT STRINGs with many fragments to an application using an affected pyasn1 decoder. The CPU consumption grows quadratically with the number of fragments, potentially exhausting decoding threads or workers. There is no impact on confidentiality or integrity. The vulnerability requires that untrusted input reaches the vulnerable decoder path and that input limits allow enough fragments. The severity is high with a CVSS v3.1 base score of 7.5, assuming network-exposed, unauthenticated input is automatically decoded.

Summary

In pyasn1 versions up to 0.6.4, the BER and CER decoders, as well as the schema-driven DER decoder, inefficiently handle constructed BIT STRING values composed of many fragments. The decoding process involves repeatedly shifting and copying the accumulated bit string value for each fragment, resulting in CPU time growing quadratically with the number of fragments. This can lead to CPU exhaustion and denial of service when processing sufficiently large attacker-controlled ASN.1 data. The vulnerability arises from the BitStringPayloadDecoder's use of BitString.fromOctetString with a prepend operation inside fragment loops. Although constructed BIT STRING is invalid in DER, the schema-driven DER decoder path still accepts definite-length constructed BIT STRINGs, exposing the vulnerability. The issue does not affect confidentiality or integrity but can cause denial of service by occupying decoding resources.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 16:05 UTC

Technical details

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