# CVE-2026-34520

## Summary

- **CVE ID:** CVE-2026-34520
- **Severity:** LOW
- **CVSS Score:** 9.1 (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)
- **CWE:** CWE-113
- **Published:** Apr 1, 2026
- **Last Modified:** Apr 4, 2026

## 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.

## Affected Products

- aio-libs — aiohttp (< 3.13.4)

## References

- [CNA](https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf)
- [CNA](https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4)
- [CNA](https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.46%
- **EPSS Percentile:** 38.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._