# CVE-2026-85721: AsyncHttpClient: Unbounded HTTP/1.1 response decompression enables a decompression-bomb denial of service > A malicious server can cause a Java application using AsyncHttpClient to crash via a decompression bomb, requiring an upgrade to patched versions. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/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:** Yes - **Published:** 17 Sep 2026 - **Updated:** 17 Sep 2026 - **Also known as:** DEBIAN-CVE-2026-85721, ECHO-b14e-ac13-29f3, GHSA-7grg-jcf7-rpmx, MINI-j7c4-x85w-4fr3, MINI-m8hh-phpp-vffx, MINI-ppv3-254v-fffv, MINI-r2mw-x53v-vr94, ROOT-APP-MAVEN-CVE-2026-85721, UBUNTU-CVE-2026-85721 ## What is CVE-2026-85721? CVE-2026-85721 is a high-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 2.0.0 until 2.16.1 and 3.0.12, automatic response decompression on the HTTP/1.1 path uses ChannelManager.newHttpContentDecompressor() to install Http1ContentDecompressor without a cumulative output-size limit. A hostile or compromised server, or an attacker who can alter a response in transit, can send a small gzip, deflate, or snappy response that expands across chunks until the client exhausts its heap and raises OutOfMemoryError; brotli and zstd are also affected when their optional codecs are present. In versions 3.0.8 through 3.0.10, the HTTP/2 decompressor is also unbounded, so switching protocols does not mitigate the issue on those releases. A limit applied to each decode call is insufficient because the response can be delivered as many small chunks, so the fixed implementation tracks total decompressed bytes for the whole response. This issue is fixed in versions 2.16.1 and 3.0.12. Weakness: CWE-409 (Improper Handling of Highly Compressed Data (Data Amplification)), CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-85721? 4 open source packages ship an affected version, including org.asynchttpclient:async-http-client. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.asynchttpclient:async-http-client` | Maven | From 2.0.0 | 2.16.1 | | `org.asynchttpclient:async-http-client` | Maven | From 2.0.0 | 2.16.1 | | `org.asynchttpclient:async-http-client` | Maven | From 3.0.0 | 3.0.12 | | `org.asynchttpclient:async-http-client` | Maven | From 3.0.0 | 3.0.12 | ## How do I fix CVE-2026-85721? Upgrade org.asynchttpclient:async-http-client to a fixed version for your release line: 2.16.1 or 3.0.12. ## Is CVE-2026-85721 being exploited? There is no known exploitation of CVE-2026-85721 in the wild and no public exploit code. Public exploit code: - CVE-2026-85721: offline checker for org.asynchttpclient:async-http-client against all 26 repository-level advisories. 3.x is fixed in 3.0.14. The 2.x line is end of life - its last release 2.16.1 is still affected by 5 advisories that will not be fixed. 9 of the 26 are still missing from the GitHub Advisory Database (as of 2026-10-12). (github_poc): https://github.com/xiaoqiMikko/async-http-client-check ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-85721 and fix it if it is affected. What it is: CVE-2026-85721 is a high-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-2026-85721 in the wild and no public exploit code. Affected packages and fixed versions: - org.asynchttpclient:async-http-client (Maven): affected from 2.0.0; fixed in 2.16.1 - org.asynchttpclient:async-http-client (Maven): affected from 2.0.0; fixed in 2.16.1 - org.asynchttpclient:async-http-client (Maven): affected from 3.0.0; fixed in 3.0.12 - org.asynchttpclient:async-http-client (Maven): affected from 3.0.0; fixed in 3.0.12 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-2026-85721/ (Markdown: https://insights.sbomify.com/CVE-2026-85721/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-85721 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-85721 - OSV: https://osv.dev/vulnerability/CVE-2026-85721 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-85721/ Summaries are generated and may contain mistakes; the official description above is the record.