Predictive Vulnerability Intelligence.

Product

  • Product
  • Pricing
  • Documentation

Company

  • About
  • Partnerships
  • Blog
  • Support

Legal

  • Terms
  • Privacy
  • Data Licensing

© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-34520

29
FAUCET Score

CVE-2026-34520 affects AIOHTTP, an asynchronous HTTP framework, specifically versions prior to 3.13.4, where its default C parser improperly handled null bytes and control characters within HTTP response headers. This vulnerability carries a critical CVSS score of 9.1, indicating it is easily exploitable over a network without authentication or user interaction, potentially leading to high impacts on system integrity and availability. Despite being on a "Hot List," there is currently no evidence of active exploitation, nor are public exploit codes available on platforms like Metasploit or ExploitDB. Community discussion and media coverage remain very low, with only a single mention identified.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.13.4CPE matchmatch criteria
cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

2.7LOW

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
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
LOW
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
UNREPORTED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.46%
Probability of exploitation in next 30 days
EPSS Percentile
37.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0046 is in the 15th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

pippatch availablevia ghsa
Product: aiohttpFixed in: 3.13.4

Vendor Advisories (1)

pipGHSA-63hf-3vf5-4wqflow

AIOHTTP's C parser (llhttp) accepts null bytes and control characters in response header values - header injection/security bypass

Apr 1, 2026

References

github.com / aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4
Patch
github.com / aio-libs/aiohttp/releases/tag/v3.13.4
Release Notes
github.com / aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf
PatchVendor Advisory