CVE-2026-126191

What it is

Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 3.0, the CSS_ESCAPES and IDENTIFIER regular-expression subpatterns can backtrack exponentially on runs of ambiguous digit escapes in an attribute-name or tag position of an otherwise valid selector. The failure occurs during selector compilation through soupsieve.compile() or Beautiful Soup select() before SELECTOR_LIMIT is applied, so an application that accepts untrusted selector strings can have a worker stalled by a short input. This issue is fixed in version 3.0.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of service disruption.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-11-10 20:07 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-11-12 17:17 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-11-12 19:09 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: not scored yet.
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-11-12 17:17 UTC

Last modified

2026-11-12 19:09 UTC

Weakness

CWE-1333

Record status

Awaiting Analysis

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-126191.md and follow it. Check whether this project is affected by CVE-2026-126191. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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