# CVE-2026-69213: Http4s Ember HTTP/2: unbounded outbound frame queue > An unauthenticated attacker can exhaust server memory by sending HTTP/2 frames that fill an unbounded outbound queue, causing a denial of service. - **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:** 15 Sep 2026 - **Updated:** 17 Sep 2026 - **Also known as:** GHSA-8f3q-3jmv-7prw ## What is CVE-2026-69213? CVE-2026-69213 is a high-severity denial of service vulnerability in http4s, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, Ember HTTP/2 serializes outbound frames through one unbounded queue consumed by writeLoop. When the peer stops reading, an unauthenticated HTTP/2 client can continue sending PING, SETTINGS, or DATA frames that cause Ember to enqueue acknowledgments or WINDOW_UPDATE frames faster than the writer drains them, exhausting heap memory on a server built with withHttp2. The shared behavior also affects an ember-client connected to a hostile HTTP/2 server, and the patch replaces the unbounded path with bounded, backpressured outbound queues. This issue is fixed in versions 0.23.35 and 1.0.0-M47. Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption) ## Which versions are affected by CVE-2026-69213? 10 open source packages ship an affected version, including org.http4s:http4s-ember-core_2.13, org.http4s:http4s-ember-core_2.12 and org.http4s:http4s-ember-core_3. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `org.http4s:http4s-ember-core_2.13` | Maven | All versions | 0.23.35 | | `org.http4s:http4s-ember-core_2.13` | Maven | All versions | 0.23.35 | | `org.http4s:http4s-ember-core_2.13` | Maven | From 1.0.0-M1 | 1.0.0-M47 | | `org.http4s:http4s-ember-core_2.13` | Maven | From 1.0.0-M1 | 1.0.0-M47 | | `org.http4s:http4s-ember-core_2.12` | Maven | All versions | 0.23.35 | | `org.http4s:http4s-ember-core_2.12` | Maven | All versions | 0.23.35 | | `org.http4s:http4s-ember-core_3` | Maven | All versions | 0.23.35 | | `org.http4s:http4s-ember-core_3` | Maven | All versions | 0.23.35 | | `org.http4s:http4s-ember-core_3` | Maven | From 1.0.0-M1 | 1.0.0-M47 | | `org.http4s:http4s-ember-core_3` | Maven | From 1.0.0-M1 | 1.0.0-M47 | ## How do I fix CVE-2026-69213? Upgrade org.http4s:http4s-ember-core_2.13 to a fixed version for your release line: 0.23.35 or 1.0.0-M47. ## Is CVE-2026-69213 being exploited? There is no known exploitation of CVE-2026-69213 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-69213 and fix it if it is affected. What it is: CVE-2026-69213 is a high-severity denial of service vulnerability in http4s, published on 15 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-2026-69213 in the wild and no public exploit code. Affected packages and fixed versions: - org.http4s:http4s-ember-core_2.13 (Maven): affected all versions; fixed in 0.23.35 - org.http4s:http4s-ember-core_2.13 (Maven): affected all versions; fixed in 0.23.35 - org.http4s:http4s-ember-core_2.13 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47 - org.http4s:http4s-ember-core_2.13 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47 - org.http4s:http4s-ember-core_2.12 (Maven): affected all versions; fixed in 0.23.35 - org.http4s:http4s-ember-core_2.12 (Maven): affected all versions; fixed in 0.23.35 - org.http4s:http4s-ember-core_3 (Maven): affected all versions; fixed in 0.23.35 - org.http4s:http4s-ember-core_3 (Maven): affected all versions; fixed in 0.23.35 - org.http4s:http4s-ember-core_3 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47 - org.http4s:http4s-ember-core_3 (Maven): affected from 1.0.0-M1; fixed in 1.0.0-M47 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-2026-69213/ (Markdown: https://insights.sbomify.com/CVE-2026-69213/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-69213 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-69213 - OSV: https://osv.dev/vulnerability/CVE-2026-69213 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-69213/ Summaries are generated and may contain mistakes; the official description above is the record.