VulnerabilityPublished 20 Sep 2026Updated 30 Oct 2026

CVE-2026-86000: Soup Sieve · Polynomial-time ReDoS (O(n²)) in the `IDENTIFIER` / `VALUE` selector sub-patterns

Affects checkovSource GCVE Database

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Authoritative record:CVE-2026-86000· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.3.0_1 when convenient.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.3.0_1

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

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

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: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 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

Upgrade checkov to 3.3.0_1.

Affected software

Product	Affected	Fixed in
Homebrewcheckov`pkg:brew/checkov`Other threats	Affected >=1.0.855 <3.3.0_1	Fixed in 3.3.0_1

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

AI-suggested

A patch is available and fixed the vulnerability in soupsieve version 3.3.0_1. Users and applications relying on soupsieve or BeautifulSoup's select methods with user-supplied selectors should upgrade to version 3.3.0_1 or later to mitigate this ReDoS vulnerability. If upgrading is not immediately possible, avoid passing untrusted input as CSS selectors to soupsieve or BeautifulSoup select functions.

Description

A Regular Expression Denial of Service (ReDoS) vulnerability exists in soupsieve's CSS selector parsing, specifically in the IDENTIFIER and VALUE sub-patterns. The flaw causes quadratic backtracking when parsing certain user-controlled selectors that fail to match, leading to excessive CPU consumption and application stalls. This affects applications using soupsieve or BeautifulSoup's select methods with user-supplied selectors. The issue is fixed in soupsieve version 3.3.0_1.

Impact

An attacker can supply specially crafted CSS selectors that cause soupsieve's regex engine to perform excessive backtracking, leading to high CPU usage and denial of service by stalling the interpreter for seconds to minutes depending on selector length. This impacts availability of applications that accept user-controlled selectors for scraping, querying, or extraction. There is no impact on confidentiality or integrity. No known exploits in the wild have been reported.

Summary

Soupsieve compiles CSS selectors using hand-written regex patterns where the IDENTIFIER sub-pattern contains two adjacent quantified groups over overlapping character classes. This creates a canonical quadratic backtracking scenario when parsing selectors with long identifier or attribute value runs that ultimately fail to match (e.g., unterminated attribute values). The backtracking causes O(n²) parse time, resulting in significant CPU delays for selectors of a few kilobytes or more. This vulnerability is exploitable when user-controlled selectors are passed to soupsieve or BeautifulSoup's select functions. The issue is confirmed in soupsieve versions up to but not including 3.3.0_1 and is reproducible on Python 3.11 and 3.14.

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Description

AI analysisMachine-generated, updated 30 Oct 2026, 18:05 UTC

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