# CVE-2026-85718: AsyncHttpClient: Connection permit leak on TLS handshake failure causes per-host denial of service

> Attackers can cause per-host denial of service in AsyncHttpClient by triggering TLS handshake failures, leaking connection permits when limits are configured.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-gcmv-gr82-6m8v, UBUNTU-CVE-2026-85718

## What is CVE-2026-85718?

CVE-2026-85718 is a medium-severity denial of service vulnerability in AsyncHttpClient async-http-client, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-85718?


## How do I fix CVE-2026-85718?

No fix has been published for CVE-2026-85718 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-85718 being exploited?

There is no known exploitation of CVE-2026-85718 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-85718 and fix it if it is affected.

What it is: CVE-2026-85718 is a medium-severity denial of service vulnerability in AsyncHttpClient async-http-client, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-85718 in the wild and no public exploit code.

Affected product: AsyncHttpClient async-http-client. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-85718/ (Markdown: https://insights.sbomify.com/CVE-2026-85718/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-85718
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-85718
- OSV: https://osv.dev/vulnerability/CVE-2026-85718

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-85718/
Summaries are generated and may contain mistakes; the official description above is the record.