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CVE-2025-57804

CVE-2025-57804 · h2 allows HTTP Request Smuggling due to illegal characters in headers

This page contains facts from public vulnerability sources. Check the original advisory before updating.

h2 is a pure-Python implementation of a HTTP/2 protocol stack. Prior to version 4.3.0, an HTTP/2 request splitting vulnerability allows attackers to perform request smuggling attacks by injecting CRLF characters into headers. This occurs when servers downgrade HTTP/2 requests to HTTP/1.1 without properly validating header names/values, enabling attackers to manipulate request boundaries and bypass security controls. This issue has been patched in version 4.3.0.

CVSS 6.9 · Medium · EPSS 1.9% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • h2

    Versions
    • < 4.3.0: Affected

    No fix published

  • python-h2 Debian:12

    Versions
    • 4.1.0-4
    • 4.2.0-1
    • 4.3.0-1
    • 4.3.0-2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Debian:13

    Versions
    • 4.2.0-1
    • 4.3.0-1
    • 4.3.0-2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Debian:14

    Versions
    • 4.2.0-1
    Affected ranges
    • ECOSYSTEM: < 4.3.0-1

    Update to 4.3.0-1

  • h2 PyPI

    Versions
    • 0.1.0
    • 1.0.0
    • 1.1.0
    • 1.1.1
    • 2.0.0
    • 2.1.0
    • 2.1.1
    • 2.1.2
    • 2.1.3
    • 2.1.4
    • 2.1.5
    • 2.2.0
    • 2.2.1
    • 2.2.2
    • 2.2.3
    • 2.2.4
    • 2.2.5
    • 2.2.6
    • 2.2.7
    • 2.3.0
    • 2.3.1
    • 2.3.2
    • 2.3.3
    • 2.3.4
    • 2.4.0
    • 2.4.1
    • 2.4.2
    • 2.4.3
    • 2.4.4
    • 2.5.0
    • 2.5.1
    • 2.5.2
    • 2.5.3
    • 2.5.4
    • 2.6.0
    • 2.6.1
    • 2.6.2
    • 3.0.0
    • 3.0.1
    • 3.1.0
    • 3.1.1
    • 3.2.0
    • 4.0.0
    • 4.1.0
    • 4.2.0
    Affected ranges
    • ECOSYSTEM: < 4.3.0

    Update to 4.3.0

  • python-h2 Ubuntu:18.04:LTS

    Versions
    • 3.0.1-1
    • 3.0.1-2
    • 3.0.1-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Ubuntu:20.04:LTS

    Versions
    • 3.0.1-4
    • 3.0.1-4.1ubuntu1
    • 3.0.1-5
    • 3.1.1-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Ubuntu:22.04:LTS

    Versions
    • 4.0.0-3
    • 4.1.0-3ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Ubuntu:24.04:LTS

    Versions
    • 4.1.0-4
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Ubuntu:25.10

    Versions
    • 4.1.0-4
    • 4.2.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-h2 Ubuntu:26.04:LTS

    Versions
    • 4.2.0-1
    • 4.3.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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