CVE-2026-85718
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.
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
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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS: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 Medium
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
async-http-clientUbuntu: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-clientUbuntu:16.04:LTS |
All versions, plus listed versions 1.6.5-4 |
None known |
async-http-clientUbuntu:18.04:LTS |
All versions, plus listed versions 1.6.5-41.6.5-5 |
None known |
async-http-clientUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 2.6.0-12.6.0-1ubuntu0.1~esm1 |
None known |
async-http-clientUbuntu: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-clientUbuntu:24.04:LTS |
All versions, plus listed versions 2.12.3-12.12.3-1ubuntu0.24.04.1 |
None known |
async-http-clientUbuntu:26.10 |
All versions, plus listed versions 2.12.3-1ubuntu1 |
None known |
async-http-clientUbuntu:26.04:LTS |
All versions, plus listed versions 2.12.3-12.12.3-1ubuntu12.12.3-1ubuntu1.1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE 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
github.com/AsyncHttpClient/async-http-client/security/advisories/GHSA-gcmv-gr82-6m8v
github.com/AsyncHttpClient/async-http-client/issues/2189
github.com/AsyncHttpClient/async-http-client/pull/2288
github.com/AsyncHttpClient/async-http-client/commit/64eb57af52a003ae7f29a2f9f4502271bbb138dd
github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85718.json
nvd.nist.gov/vuln/detail/CVE-2026-85718
ubuntu.com/security/CVE-2026-85718
cve.org/CVERecord?id=CVE-2026-85718