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CVE-2026-85718

AsyncHttpClient: Connection permit leak on TLS handshake failure causes per-host denial of service

5.9 Medium

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 3.0.8 until 3.0.12, a client with maxConnections or maxConnectionsPerHost set above zero leaks one connection permit whenever TLS connection establishment fails before the handshake completes. NettyConnectListener removes the partitionKeyLock permit from NettyResponseFuture before every failure path is bound to the channel closeFuture, so an abort can leave the permit unreleased. Repeated failures can permanently lock out one host under a per-host limit or drain the shared pool under a global limit, blocking later requests even when no connection remains open. The default unlimited connection setting is not affected. This issue is fixed in version 3.0.12.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.53%Up 0.2 points since Sep 18, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.9

AsyncHttpClient: Connection permit leak on TLS handshake failure causes per-host denial of service

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 3.0.8 until 3.0.12, a client with maxConnections or maxConnectionsPerHost set above zero leaks one connection permit whenever TLS connection establishment fails before the handshake completes. NettyConnectListener removes the partitionKeyLock permit from NettyResponseFuture before every failure path is bound to the channel closeFuture, so an abort can leave the permit unreleased. Repeated failures can permanently lock out one host under a per-host limit or drain the shared pool under a global limit, blocking later requests even when no connection remains open. The default unlimited connection setting is not affected. This issue is fixed in version 3.0.12.

Record
CVE-2026-85718
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
EUVDEUVD-2026-81908 5.9

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 3.0.8 until 3.0.12, a client with maxConnections or maxConnectionsPerHost set above zero leaks one connection permit whenever TLS connection establishment fails before the handshake completes. NettyConnectListener removes the partitionKeyLock permit from NettyResponseFuture before every failure path is bound to the channel closeFuture, so an abort can leave the permit unreleased. Repeated failures can permanently lock out one host under a per-host limit or drain the shared pool under a global limit, blocking later requests even when no connection remains open. The default unlimited connection setting is not affected. This issue is fixed in version 3.0.12.

Record
EUVD-2026-81908
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
NVD 5.9

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 3.0.8 until 3.0.12, a client with maxConnections or maxConnectionsPerHost set above zero leaks one connection permit whenever TLS connection establishment fails before the handshake completes. NettyConnectListener removes the partitionKeyLock permit from NettyResponseFuture before every failure path is bound to the channel closeFuture, so an abort can leave the permit unreleased. Repeated failures can permanently lock out one host under a per-host limit or drain the shared pool under a global limit, blocking later requests even when no connection remains open. The default unlimited connection setting is not affected. This issue is fixed in version 3.0.12.

Record
CVE-2026-85718
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
OSV 5.9

AsyncHttpClient: Connection permit leak on TLS handshake failure causes per-host denial of service

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 3.0.8 until 3.0.12, a client with maxConnections or maxConnectionsPerHost set above zero leaks one connection permit whenever TLS connection establishment fails before the handshake completes. NettyConnectListener removes the partitionKeyLock permit from NettyResponseFuture before every failure path is bound to the channel closeFuture, so an abort can leave the permit unreleased. Repeated failures can permanently lock out one host under a per-host limit or drain the shared pool under a global limit, blocking later requests even when no connection remains open. The default unlimited connection setting is not affected. This issue is fixed in version 3.0.12.

Record
CVE-2026-85718
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400, CWE-772
Updated
2026-11-02
OSVUBUNTU-CVE-2026-85718 5.9

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. From 3.0.8 until 3.0.12, a client with maxConnections or maxConnectionsPerHost set above zero leaks one connection permit whenever TLS connection establishment fails before the handshake completes. NettyConnectListener removes the partitionKeyLock permit from NettyResponseFuture before every failure path is bound to the channel closeFuture, so an abort can leave the permit unreleased. Repeated failures can permanently lock out one host under a per-host limit or drain the shared pool under a global limit, blocking later requests even when no connection remains open. The default unlimited connection setting is not affected. This issue is fixed in version 3.0.12.

Record
UBUNTU-CVE-2026-85718
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
async-http-client
Ubuntu:Pro:14.04:LTS
All versions, plus listed versions
1.6.5-11.6.5-21.6.5-2ubuntu0.1~esm1
None known
async-http-client
Ubuntu:16.04:LTS
All versions, plus listed versions
1.6.5-4
None known
async-http-client
Ubuntu:18.04:LTS
All versions, plus listed versions
1.6.5-41.6.5-5
None known
async-http-client
Ubuntu:Pro:20.04:LTS
All versions, plus listed versions
2.6.0-12.6.0-1ubuntu0.1~esm1
None known
async-http-client
Ubuntu:22.04:LTS
All versions, plus listed versions
2.12.2-12.12.3-12.12.3-1ubuntu0.22.04.1
None known
async-http-client
Ubuntu:24.04:LTS
All versions, plus listed versions
2.12.3-12.12.3-1ubuntu0.24.04.1
None known
async-http-client
Ubuntu:26.10
All versions, plus listed versions
2.12.3-1ubuntu1
None known
async-http-client
Ubuntu:26.04:LTS
All versions, plus listed versions
2.12.3-12.12.3-1ubuntu12.12.3-1ubuntu1.1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-85718 is a medium vulnerability (CVSS 5.9) in Asynchttpclient Async-http-client, published September 17, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.53%, the 45th percentile. No source names a fixed version.

References

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