How severe is CVE-2025-53643?

No CVSS score has been assigned to CVE-2025-53643 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-53643?

CVE-2025-53643 affects the following packages: aiohttp (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-53643?

Update aiohttp to 3.12.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-53643 is resolved across your whole dependency graph.

How do I detect CVE-2025-53643 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-53643 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2025-53643 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-53643 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-53643?

CVE-2025-53643 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 29th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-53643?

CVE-2025-53643 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-53643 published, and has it been updated?

CVE-2025-53643 was published on July 14, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2025-53643 — aiohttp

Fix: aio-libs/aiohttp@e8d774f

CVE-2025-53643 is a CWE-444 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

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

Also known asGHSA-9548-qrrj-x5pjPYSEC-2026-1104

Published

Jul 14, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 31, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-53643.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk+0.04%

Lower risk than most CVEs29th percentile — riskier than 29% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍aiohttp

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.12.14, the Python parser is vulnerable to a request smuggling vulnerability due to not parsing trailer sections of an HTTP request. If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections. Version 3.12.14 contains a patch for this issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`aiohttp`	all versions	3.12.14`pip install --upgrade 'aiohttp==3.12.14'`

Affected Products

1 product · 1 configurations

Application

aiohttpaiohttp

< 3.12.14

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update aiohttp to 3.12.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-53643 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow

A low impact HTTP request smuggling flaw was found in the aiohttp Python library, which is shipped in a number of Red Hat offerings, including Red Hat Ansible Automation Platform, Red Hat OpenShift AI, and Red Hat Enterprise Linux AI. The pure-Python HTTP parser in aiohttp does not parse trailer sections of an HTTP…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2025-53643 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Ansible Automation Platform 2.5 for RHEL 8	`automation-controller-0:4.6.25-1.el8ap`	RHSA-2026:1506
Red Hat Ansible Automation Platform 2.6 for RHEL 9	`automation-controller-0:4.7.8-1.el9ap`	RHSA-2026:1249
Red Hat Satellite 6.18 for RHEL 9	`python3.12-aiohttp-0:3.13.3-1.el9pc`	RHSA-2026:2760
Red Hat Ansible Automation Platform 2.6	`ansible-automation-platform-26/ee-supported-rhel9:1772508458`	RHSA-2026:3960
Red Hat OpenShift AI 2.22	`rhoai/odh-feature-server-rhel9:v2.22.3-1763565765`	RHSA-2025:22759
Red Hat OpenShift AI 2.25	`rhoai/odh-feature-server-rhel9:v2.25.1-1765354568`	RHSA-2025:23531
Red Hat OpenShift Service Mesh 3.0	`openshift-service-mesh/istio-proxyv2-rhel9:1.24.6-1764181669`	RHSA-2025:22939
Red Hat OpenShift Service Mesh 3.1	`openshift-service-mesh/istio-proxyv2-rhel9:1.26.6-1764332723`	RHSA-2025:22944

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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