CVE
Soup Sieve denial of service via :has() sibling combinator
- Exploited
- Proof of concept public, per CISA
- Fix
- Fixed in 2.10
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.10.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- FIRST's estimate of the chance attackers exploit it in the next 30 days, updated daily.What do these mean? →
- 0.48% · 41st percentile
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 58/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: poc
- Automatable: no
- Technical impact: partial
Summary
Soup Sieve, a CSS selector library used with Beautiful Soup 4, can be made to take minutes of processing time by a small crafted HTML document when a developer-written selector uses the general sibling combinator inside :has(). An attacker can reach this remotely, without logging in, by submitting such markup to an application that evaluates that selector over untrusted HTML.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.10, matching a developer-authored selector that places the general sibling combinator inside :has() repeatedly scans each candidate element's following siblings when the right-hand side is absent, producing quadratic work on attacker-controlled HTML. Applications that evaluate a fixed selector such as div:has(a ~ b) over untrusted markup can have a worker occupied for minutes by a small document, while the adjacent sibling form and trusted-only document processing are not affected in the same way. This issue is fixed in version 2.10.
cve.now Index
- Exploitation15/40CISA rates a proof of concept as public
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach20/20soupsieve: 81.9M downloads a week
- Severity6.3/10CVSS 6.3
- No patch0/5No signal
What would change the score
- Would score about 88 if added to CISA KEV
- Would score about 83 if CISA's SSVC rates exploitation active
- Would score about 63 if advisories confirm default setups are exposed
Impact
- Widely used
soupsieve has 81.9m weekly downloads.Source: pypistats.org
34.5k packages depend on soupsieve.Source: deps.dev
What to do
Upgrade to a fixed version: 2.10.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126192 (Soup Sieve: General sibling combinator inside :has() matches untrusted HTML in quadratic time), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-126192 (entry last updated 2026-11-13):
Affected:
- facelessuser soupsieve: fixed in 2.10
- PyPI package soupsieve: fixed in 2.10.0
Fixed versions: 2.10.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-126192 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126192 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Packages (PyPI): find every lockfile in each project and run the stack.check operation of the cve.now MCP server (execute) on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/facelessuser/soupsieve/security/advisories/GHSA-4j63-6c4x-wfg4
- https://github.com/facelessuser/soupsieve/pull/304
- https://github.com/facelessuser/soupsieve/commit/ffb88cca745c591224f74a8e86414a85e8f35fc0
- https://github.com/facelessuser/soupsieve/releases/tag/2.10
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-126192
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126192"}.Timeline
- CVE published
- First seen by cve.now1 day
- CISA SSVC assessment
Exploitation: poc · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- facelessuser soupsieve
fixed in 2.10
- soupsievePyPI
fixed in 2.10.0
Fixed in 2.10.0 (released Sep 24, 2026, 49 days before disclosure).
The latest release, 4.1.0, is not affected.
Evidence 6
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 3
- Repository
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-126192
Is CVE-2026-126192 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-126192?
soupsieve: before 2.10. soupsieve (PyPI): before 2.10.0.Source: cve.now feed data
How do I fix CVE-2026-126192?
Upgrade to a fixed version: 2.10.Source: cve.now feed data