CVE-2025-53643: PYSEC-2026-1104 - AIOHTTP is vulnerable to HTTP Request/Response Smuggling through incorrect parsing of chunked trailer sections

CVE-2025-53643 · Severity: medium · CVSS 4 · Published 2026-07-07

AIOHTTP is vulnerable to HTTP Request/Response Smuggling through incorrect parsing of chunked trailer sections

Technologies: aiohttp (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2025-53643 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-53643 being exploited in the wild.
How severe is CVE-2025-53643?
Medium severity, with a CVSS score of 4, published 7 July 2026.
Which products and versions are affected?
aiohttp (PyPI) ECOSYSTEM:introduced=0,fixed=3.12.14.
Is there a fix for CVE-2025-53643?
Yes. aiohttp (PyPI): upgrade to 3.12.14 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-53643?
Check whether you run aiohttp (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • aiohttp (PyPI): upgrade to 3.12.14 or later
    pip install "aiohttp>=3.12.14"

Affected products

  • aiohttp (PyPI) ECOSYSTEM:introduced=0,fixed=3.12.14

Identifiers

  • CVE-2025-53643
  • GHSA-9548-qrrj-x5pj
  • PYSEC-2026-1104

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