Is CVE-2026-34520 actively exploited?

CVE-2026-34520 has no public evidence of in-the-wild exploitation as of 2026-04-16.

What is the CVSS score for CVE-2026-34520?

CVE-2026-34520 has a CVSS score of 2.7 (LOW severity). Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X.

How do I patch CVE-2026-34520?

Patch guidance is available from aiohttp security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2026-34520.

CVE-2026-34520 - remediation guidance & executive summary

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser (the default for most installs) accepted null bytes and control characters in response headers. This issue has been patched in version 3.13.4.

CVSS Metrics

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector: network
Complexity: low
Privileges: none
User Action: none
Confidentiality: undefined
Integrity: undefined
Availability: undefined
Weaknesses: CWE-113

Metadata

Primary Vendor: AIOHTTP
Published: 4/1/2026
Last Modified: 4/16/2026
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

Affected Products

aiohttp : aiohttp

Remediation Guidance

Executive Summary

Cite this page

CVE-2026-34520. CVEDatabase.com. Retrieved 1 May 2026. https://cvedatabase.com/cve/CVE-2026-34520

View on NIST NVD

CVE-2026-34520 vulnerability