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CVE-2026-97688

CVE-2026-97688 · urllib3: Chunked Deflate streaming can enter an infinite loop

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

urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.

CVSS 6.9 · Medium · EPSS 0.3% · Fix available

Published
Updated

Stack: system · python

Affected products and versions

  • urllib3

    Versions
    • >= 2.6.2, < 2.8.0: Affected

    No fix published

  • python-urllib3 Debian:14

    Versions
    • 2.3.0-3
    • 2.5.0-1
    • 2.5.0-1.1
    • 2.5.0-2
    • 2.6.3-1
    • 2.6.3-2
    • 2.7.0-1
    • 2.7.0-2
    • 2.7.0-3
    Affected ranges
    • ECOSYSTEM: < 2.8.0-1

    Update to 2.8.0-1

  • urllib3 PyPI

    Versions
    • 2.6.2
    • 2.6.3
    • 2.7.0
    Affected ranges
    • ECOSYSTEM: ≥ 2.6.2, < 2.8.0

    Update to 2.8.0

  • python-pip Ubuntu:Pro:14.04:LTS

    Versions
    • 1.4.1-2
    • 1.5.4-1
    • 1.5.4-1ubuntu1
    • 1.5.4-1ubuntu3
    • 1.5.4-1ubuntu4
    • 1.5.4-1ubuntu4+esm1
    • 1.5.4-1ubuntu4+esm2
    • 1.5.4-1ubuntu4+esm3
    • 1.5.4-1ubuntu4+esm4
    • 1.5.4-1ubuntu4+esm5
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-pip Ubuntu:Pro:16.04:LTS

    Versions
    • 1.5.6-7ubuntu1
    • 1.5.6-7ubuntu2
    • 8.0.2-7
    • 8.0.3-1
    • 8.0.3-2
    • 8.1.0-1
    • 8.1.0-2
    • 8.1.1-1
    • 8.1.1-2
    • 8.1.1-2ubuntu0.1
    • 8.1.1-2ubuntu0.2
    • 8.1.1-2ubuntu0.4
    • 8.1.1-2ubuntu0.6
    • 8.1.1-2ubuntu0.6+esm2
    • 8.1.1-2ubuntu0.6+esm3
    • 8.1.1-2ubuntu0.6+esm4
    • 8.1.1-2ubuntu0.6+esm5
    • 8.1.1-2ubuntu0.6+esm6
    • 8.1.1-2ubuntu0.6+esm8
    • 8.1.1-2ubuntu0.6+esm10
    • 8.1.1-2ubuntu0.6+esm11
    • 8.1.1-2ubuntu0.6+esm12
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-pip Ubuntu:Pro:18.04:LTS

    Versions
    • 9.0.1-2
    • 9.0.1-2.3~ubuntu1
    • 9.0.1-2.3~ubuntu1.18.04.1
    • 9.0.1-2.3~ubuntu1.18.04.2
    • 9.0.1-2.3~ubuntu1.18.04.3
    • 9.0.1-2.3~ubuntu1.18.04.4
    • 9.0.1-2.3~ubuntu1.18.04.5
    • 9.0.1-2.3~ubuntu1.18.04.5+esm2
    • 9.0.1-2.3~ubuntu1.18.04.5+esm3
    • 9.0.1-2.3~ubuntu1.18.04.6
    • 9.0.1-2.3~ubuntu1.18.04.6+esm1
    • 9.0.1-2.3~ubuntu1.18.04.7
    • 9.0.1-2.3~ubuntu1.18.04.7+esm1
    • 9.0.1-2.3~ubuntu1.18.04.8
    • 9.0.1-2.3~ubuntu1.18.04.8+esm1
    • 9.0.1-2.3~ubuntu1.18.04.8+esm2
    • 9.0.1-2.3~ubuntu1.18.04.8+esm4
    • 9.0.1-2.3~ubuntu1.18.04.8+esm6
    • 9.0.1-2.3~ubuntu1.18.04.8+esm7
    • 9.0.1-2.3~ubuntu1.18.04.8+esm8
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-pip Ubuntu:Pro:20.04:LTS

    Versions
    • 18.1-5
    • 18.1-5build1
    • 18.1-5ubuntu1
    • 20.0.2-2
    • 20.0.2-4
    • 20.0.2-5
    • 20.0.2-5ubuntu1
    • 20.0.2-5ubuntu1.1
    • 20.0.2-5ubuntu1.3
    • 20.0.2-5ubuntu1.4
    • 20.0.2-5ubuntu1.5
    • 20.0.2-5ubuntu1.6
    • 20.0.2-5ubuntu1.7
    • 20.0.2-5ubuntu1.8
    • 20.0.2-5ubuntu1.9
    • 20.0.2-5ubuntu1.10
    • 20.0.2-5ubuntu1.10+esm2
    • 20.0.2-5ubuntu1.11
    • 20.0.2-5ubuntu1.11+esm2
    • 20.0.2-5ubuntu1.11+esm3
    • 20.0.2-5ubuntu1.11+esm4
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-pip Ubuntu:Pro:22.04:LTS

    Versions
    • 20.3.4-4
    • 21.3.1+dfsg-3
    • 22.0.2+dfsg-1
    • 22.0.2+dfsg-1ubuntu0.1
    • 22.0.2+dfsg-1ubuntu0.2
    • 22.0.2+dfsg-1ubuntu0.3
    • 22.0.2+dfsg-1ubuntu0.4
    • 22.0.2+dfsg-1ubuntu0.5
    • 22.0.2+dfsg-1ubuntu0.6
    • 22.0.2+dfsg-1ubuntu0.7
    • 22.0.2+dfsg-1ubuntu0.7+esm1
    • 22.0.2+dfsg-1ubuntu0.7+esm2
    • 22.0.2+dfsg-1ubuntu0.7+esm3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-pip Ubuntu:Pro:24.04:LTS

    Versions
    • 23.2+dfsg-1
    • 23.3+dfsg-1
    • 24.0+dfsg-1
    • 24.0+dfsg-1ubuntu1
    • 24.0+dfsg-1ubuntu1.1
    • 24.0+dfsg-1ubuntu1.2
    • 24.0+dfsg-1ubuntu1.3
    • 24.0+dfsg-1ubuntu1.3+esm1
    • 24.0+dfsg-1ubuntu1.3+esm2
    • 24.0+dfsg-1ubuntu1.3+esm3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-pip Ubuntu:26.10

    Versions
    • 25.1.1+dfsg-1ubuntu2
    • 26.1.2+dfsg-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • python-urllib3 Ubuntu:26.04:LTS

    Versions
    • 2.3.0-3
    • 2.5.0-1
    • 2.5.0-1ubuntu1
    • 2.5.0-1ubuntu2
    • 2.6.3-1ubuntu1
    • 2.6.3-1ubuntu1.1
    Affected ranges
    • ECOSYSTEM: < 2.6.3-1ubuntu1.2

    Update to 2.6.3-1ubuntu1.2

  • python-pip Ubuntu:Pro:26.04:LTS

    Versions
    • 25.1.1+dfsg-1ubuntu2
    • 25.1.1+dfsg-1ubuntu2+esm1
    • 25.1.1+dfsg-1ubuntu2+esm2
    • 25.1.1+dfsg-1ubuntu2+esm3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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