CVE-2025-6069: HTMLParser quadratic complexity when processing malformed inputs

Published Jun 17, 2025
·
Updated

HTMLParser quadratic complexity when processing malformed inputs

Other sources

The html.parser.HTMLParser class had worse-case quadratic complexity when processing certain crafted malformed inputs potentially leading to amplified denial-of-service.

NVD

Affected Software

5 affected componentsFixes available
python/html.parser
Microsoft cbl2 python3 3.9.19-13<3.9.19-14
3.9.19-14
Microsoft azl3 python3 3.12.9-3<3.12.9-3
3.12.9-3
Microsoft cbl2 python3 3.9.19-14<3.9.19-14
3.9.19-14
IBM Netezza Software<=11.3.0.3-IF2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 3.9.19-14
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 3.12.9-3

Event History

Jun 17, 2025
CVE Published
via MITRE·01:39 PM
Data Sourced
via MITRE·01:39 PM
DescriptionSeverityWeakness
Data Sourced
via NVD·02:15 PM
DescriptionSeverityWeakness
Data Sourced
via Red Hat·04:12 PM
DescriptionSeverityAffected Software
Jul 18, 2025
Data Sourced
via Microsoft·07:00 AM
DescriptionSeverityWeakness
Data Sourced
via Microsoft·07:00 AM
Affected Software
Updated
via Microsoft·07:00 AM
Affected Software
Updated
via Microsoft·07:00 AM
DescriptionSeverity
Aug 20, 2026
Data Sourced
via IBM·12:00 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is the severity of CVE-2025-6069?

CVE-2025-6069 is a denial-of-service vulnerability with potential for severe impact due to its quadratic complexity when processing malformed inputs.

2

How can I fix CVE-2025-6069?

To fix CVE-2025-6069, update to the latest version of the Python html.parser library where the vulnerability has been addressed.

3

What kind of attacks does CVE-2025-6069 enable?

CVE-2025-6069 enables denial-of-service attacks by allowing crafted inputs to cause excessive processing time.

4

Which software is affected by CVE-2025-6069?

CVE-2025-6069 specifically affects the Python html.parser class.

5

What are the potential consequences of CVE-2025-6069?

The consequences of CVE-2025-6069 include application crashes and unavailability due to resource exhaustion.

Contact

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