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Soup SieveApplication · Facelessuser

CVE-2026-49476

HIGH · 7.5 CVSS v3.1 Published 2026-07-14
Fix available
A fix is available. Upgrade to 2.8.4 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Soup Sieve is a CSS selector library designed to be used with Beautiful Soup 4. Prior to 2.8.4, the CSS selector parser in soupsieve allocates unbounded memory when compiling large comma-separated selector lists, allowing an attacker who can supply a crafted selector string to soupsieve.compile() or Beautiful Soup .select() / .select_one() to allocate hundreds of megabytes of heap memory from a relatively small input and cause denial of service. This issue is fixed in version 2.8.4.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Soup Sieve's CSS selector parser in versions prior to 2.8.4 allocates unbounded memory when processing large comma-separated selector lists. A crafted selector string can cause the parser to allocate hundreds of megabytes of heap memory from relatively small input, leading to denial of service.

MitigationUpgrade Soup Sieve to version 2.8.4 or later to resolve the unbounded memory allocation vulnerability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Soup SieveApplication
Affected:< 2.8.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Beautiful Soup version
    Run 'pip show beautifulsoup4' or 'python -c "import bs4; print(bs4.__version__)"'
    Affected if Version is lower than 4.12.0 (which bundles soupsieve 2.8.4) or soupsieve version is below 2.8.4
  2. Identify soupsieve version directly
    Run 'pip show soupsieve' or 'python -c "import soupsieve; print(soupsieve.__version__)"'
    Affected if Version is lower than 2.8.4
  3. Check application code for .select()/.select_one() usage with external input
    Search source code for patterns like '.select(' and '.select_one(' and verify if the argument comes from user request parameters, API input, or any untrusted source
    Affected if User-controlled input flows directly into .select() or .select_one() without sanitization
  4. Check for soupsieve.compile() usage with external input
    Search source code for 'soupsieve.compile(' and verify if the selector argument originates from untrusted sources
    Affected if User input flows to soupsieve.compile() without validation
  5. Review selector input handling and length limits
    Inspect any validation logic applied to selector strings before passing to parsing functions
    Affected if No length limits or validation is performed on selector strings before parsing

You are affected if soupsieve version is below 2.8.4 (or Beautiful Soup 4 is below 12.0 which bundles the fixed version) AND your application passes untrusted input to .select(), .select_one(), or soupsieve.compile().

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.8.4 or later
Fixed in 2.8.4
Interim mitigation

Upgrade Soup Sieve to version 2.8.4 or later to resolve the unbounded memory allocation vulnerability.

Recommended fix High confidence

soupsieve version 2.8.4 or later

  1. Check the current version of soupsieve installed by running: pip show soupsieve or pip freeze | grep soupsieve
  2. Upgrade soupsieve to version 2.8.4 or later by running: pip install --upgrade soupsieve>=2.8.4
  3. Verify the upgrade was successful by running: pip show soupsieve and confirming the version is 2.8.4 or higher
  4. If using Beautiful Soup, ensure your project imports the updated soupsieve library by testing a simple .select() call

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Soup Sieve Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-49476 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data