CVE-2026-85999VulnerabilityPublished 20 Sep 2026Updated 26 Oct 2026

flexget · Soup Sieve: Polynomial-time ReDoS (O(n²))

Affects flexgetSource GCVE Database

Authoritative record:CVE-2026-85999· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.19.30 when convenient.

Data as of 26 Oct 2026, 17:27 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 48% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.19.30

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
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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 flexget to 3.19.30.

Affected software

Product	Affected	Fixed in
Homebrewflexget`pkg:brew/flexget`Other threats	Affected >=3.17.7 <3.19.30	Fixed in 3.19.30

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 in soupsieve version 3.19.30 that fixes the regex inefficiency causing the ReDoS. Users should upgrade to version 3.19.30 or later. If upgrading is not immediately possible, avoid passing user-controlled CSS selectors to soupsieve or BeautifulSoup's select functions. Applications using only hard-coded selectors are not affected.

Description

A Regular Expression Denial of Service (ReDoS) vulnerability exists in soupsieve's whitespace/comment trimming regex RE_WS_END, which is used during CSS selector parsing. The regex is unanchored at the start and uses .search(), causing quadratic time complexity (O(n²)) on valid selectors with long whitespace or comment runs not exactly at the string end. This can cause significant CPU delays (e.g., ~10 seconds for a 20 KB selector). The issue affects soupsieve versions >=3.17.7 and <3.19.30 and is exploitable when user-controlled selectors are passed to soupsieve or BeautifulSoup's select methods. A fix is available in version 3.19.30.

Impact

This vulnerability allows an attacker to cause a denial of service by providing a specially crafted but valid CSS selector containing long runs of whitespace or comments. The quadratic time complexity in regex matching leads to high CPU usage and significant delays (e.g., ~10 seconds for a 20 KB selector), potentially stalling applications that use soupsieve or BeautifulSoup's selector functions with user-controlled input. There is no impact on confidentiality or integrity, only availability (denial of service).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 17:27 UTC

Technical details

References

Community reviews

Related threats