CVE-2023-49081Public exploitNetwork attack vector

HTTP request smuggling via unvalidated version sequence

Published Nov 30, 2023 · Updated Jun 23, 2026

CRLF injection in aiohttp before 3.9.0 allows remote attackers to smuggle HTTP requests through applications that expose the version value. ClientRequest.send indexes an arbitrary sequence supplied as the HTTP version while formatting the request line, allowing a CRLF-bearing element to escape into headers. Exploitation requires attacker control of the version value and its type plus a Connection header, and permits header injection or a second request.

CVSS severity7.2
High
EPSS probability0.88%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CRLF injection in aiohttp before 3.9.0 allows remote attackers to smuggle HTTP requests through applications that expose the version value. ClientRequest.send indexes an arbitrary sequence supplied as the HTTP version while formatting the request line, allowing a CRLF-bearing element to escape into headers. Exploitation requires attacker control of the version value and its type plus a Connection header, and permits header injection or a second request.

The record

CVE
CVE-2023-49081
Published
Nov 30, 2023
Updated
Jun 23, 2026
Vendor
aio-libs
Product
aiohttp
Classifications
CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 30, 2023CVE publishedPublication date reported by the CVE source.
  2. Jun 23, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

aio-libs · aiohttpversion=< 3.9.0

Published CVSS scores

7.2GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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