CVE-2026-54275Network attack vector

TLS hostname validation bypass via pooled connection reuse

Published Jun 22, 2026 · Updated Jun 22, 2026

TLS hostname-validation bypass in aiohttp before 3.14.1 allows remote attackers to bypass certificate rejection through connection reuse. ClientRequest.connection_key omits the per-request server_hostname value, so TCPConnector treats requests with different TLS names as eligible for the same pooled connection. Reachability requires one session to contact the same domain more than once with different server_hostname values; the later request can inherit a connection authenticated only for the earlier name.

CVSS severity7.5
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

TLS hostname-validation bypass in aiohttp before 3.14.1 allows remote attackers to bypass certificate rejection through connection reuse. ClientRequest.connection_key omits the per-request server_hostname value, so TCPConnector treats requests with different TLS names as eligible for the same pooled connection. Reachability requires one session to contact the same domain more than once with different server_hostname values; the later request can inherit a connection authenticated only for the earlier name.

The record

CVE
CVE-2026-54275
Published
Jun 22, 2026
Updated
Jun 22, 2026
Vendor
aio-libs
Product
aiohttp
Classifications
CWE-297
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 22, 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=< 3.14.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

aio-libs · aiohttpversion=< 3.14.1

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
2.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U

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.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-297Improper Validation of Certificate with Host Mismatch

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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