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CVE Vulnerability Details :
CVE-2026-34520
PUBLISHED
More InfoOfficial Page
Assigner-GitHub_M
Assigner Org ID-a0819718-46f1-4df5-94e2-005712e83aaa
View Known Exploited Vulnerability (KEV) details
Published At-01 Apr, 2026 | 20:27
Updated At-04 Apr, 2026 | 03:13
Rejected At-
▼CVE Numbering Authority (CNA)
AIOHTTP: C parser (llhttp) accepts null bytes and control characters in response header values - header injection / security bypass

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
Vendor
aio-libs
Product
aiohttp
Versions
Affected
  • < 3.13.4
Problem Types
TypeCWE IDDescription
CWECWE-113CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
Type: CWE
CWE ID: CWE-113
Description: CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
Metrics
VersionBase scoreBase severityVector
4.02.7LOW
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
Version: 4.0
Base score: 2.7
Base severity: LOW
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
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf
x_refsource_CONFIRM
https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4
x_refsource_MISC
https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4
x_refsource_MISC
Hyperlink: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf
Resource:
x_refsource_CONFIRM
Hyperlink: https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4
Resource:
x_refsource_MISC
Hyperlink: https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4
Resource:
x_refsource_MISC
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
3.19.1CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Version: 3.1
Base score: 9.1
Base severity: CRITICAL
Vector:
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions
Configurations
Workarounds
Exploits
Credits
Timeline
EventDate
Replaced By
Rejected Reason
References
HyperlinkResource
Details not found