VulnerabilityPublished 13 Nov 2026

CVE-2026-126190: Soup Sieve · Polynomial-time denial of service in the descendant combinator

Affects maigretSource GCVE Database

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Authoritative record:CVE-2026-126190· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 4.0 : patch maigret soon.

Data as of 13 Nov 2026, 21:16 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

Patch: Available – fixed in 4.0

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 12 Nov 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 13 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

Affected software

Product	Affected	Fixed in
Homebrewmaigret`pkg:brew/maigret`Other threats	Affected >=0.5.0	Fixed in–

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AI-suggested

Upgrade to Soup Sieve version 4.0 or later, where the vulnerability is fixed by caching ancestor matches to ensure linear-time selector evaluation. If upgrading is not possible, reduce the use of descendant combinators in selectors applied to untrusted documents, limit the size and nesting depth of such documents, or run selector operations with time limits in isolated worker processes. Avoid using the NOCACHE flag as it reverts to vulnerable behavior.

Description

CVE-2026-126190 is a denial of service vulnerability in Soup Sieve's handling of CSS selectors with descendant combinators. The matching algorithm exhibits polynomial-time complexity relative to document nesting depth and the number of descendant combinators, causing excessive CPU usage on crafted deeply nested documents. This can tie up application workers for extended periods when processing untrusted HTML or XML. The issue is fixed in Soup Sieve 4.0 by introducing caching to reduce matching complexity to linear time.

Impact

The vulnerability enables an attacker who controls input documents to cause high CPU usage and denial of service by submitting deeply nested markup that triggers polynomial-time selector matching. This can significantly degrade or halt application functionality that uses Soup Sieve selectors with descendant combinators on untrusted content. There is no impact on confidentiality or integrity, only availability. Applications processing only trusted documents are not affected.

Summary

Soup Sieve versions prior to 4.0 suffer from a polynomial-time denial of service vulnerability when matching selectors containing descendant combinators (e.g., 'a b'). The matching process involves repeated ancestor walks without caching, resulting in time complexity of O(n^(k+1)) for a selector with k descendant combinators on a chain of n nested elements. An attacker controlling input HTML or XML can exploit this by submitting a small but deeply nested document, causing the selector matching to consume CPU resources for seconds to minutes. The vulnerability affects applications that run descendant combinator selectors on untrusted markup, such as scrapers or HTML sanitizers. The fix in version 4.0 adds caching of ancestor matches, reducing the complexity to linear time and mitigating the denial of service risk.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 21:16 UTC

Technical details

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