# CVE-2021-32778: Excessive CPU utilization when closing HTTP/2 streams > Attackers can cause excessive CPU utilization and denial of service by resetting many HTTP/2 streams in Envoy proxy deployments with high stream limits. - **Severity:** Medium 5.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 24 Aug 2021 - **Updated:** 3 Aug 2024 - **Also known as:** BIT-envoy-2021-32778, GHSA-3xh3-33v5-chcc, RHEA-2021:4051 ## What is CVE-2021-32778? CVE-2021-32778 is a medium-severity denial of service vulnerability in Envoyproxy Envoy, published on 24 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affected versions envoy’s procedure for resetting a HTTP/2 stream has O(N^2) complexity, leading to high CPU utilization when a large number of streams are reset. Deployments are susceptible to Denial of Service when Envoy is configured with high limit on H/2 concurrent streams. An attacker wishing to exploit this vulnerability would require a client opening and closing a large number of H/2 streams. Envoy versions 1.19.1, 1.18.4, 1.17.4, 1.16.5 contain fixes to reduce time complexity of resetting HTTP/2 streams. As a workaround users may limit the number of simultaneous HTTP/2 dreams for upstream and downstream peers to a low number, i.e. 100. Weakness: CWE-834 (Excessive Iteration) ## Which versions are affected by CVE-2021-32778? 1 open source package ship an affected version, including envoy. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `envoy` | Bitnami | From 1.16.0 | 1.16.5, 1.17.4, 1.18.4, 1.19.1 | | `servicemesh` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-5.el8 | | `servicemesh-cni` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-5.el8 | | `servicemesh-grafana` | Red Hat:service_mesh:2.1::el8 | All versions | 0:7.2.1-2.el8 | | `servicemesh-grafana-debuginfo` | Red Hat:service_mesh:2.1::el8 | All versions | 0:7.2.1-2.el8 | | `servicemesh-operator` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-4.el8 | | `servicemesh-pilot-agent` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-5.el8 | | `servicemesh-pilot-discovery` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-5.el8 | | `servicemesh-prometheus` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.23.0-1.el8 | | `servicemesh-proxy` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-13.el8 | | `servicemesh-proxy-debuginfo` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-13.el8 | | `servicemesh-proxy-debugsource` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-13.el8 | | `servicemesh-proxy-wasm` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-13.el8 | | `servicemesh-ratelimit` | Red Hat:service_mesh:2.1::el8 | All versions | 0:2.1.0-1.el8 | Products: Envoyproxy Envoy. ## How do I fix CVE-2021-32778? Upgrade envoy to a fixed version for your release line: 1.16.5, 1.17.4, 1.18.4 or 1.19.1. ## Is CVE-2021-32778 being exploited? There is no known exploitation of CVE-2021-32778 in the wild and no public exploit code. ## Other vulnerabilities in Envoyproxy Envoy - [CVE-2022-29226](https://insights.sbomify.com/CVE-2022-29226/): Trivial authentication bypass in Envoy (critical 10.0) - [CVE-2019-18801](https://insights.sbomify.com/CVE-2019-18801/): Memory corruption in n/a (critical 9.8) - [CVE-2019-18802](https://insights.sbomify.com/CVE-2019-18802/): Security feature bypass in n/a (critical 9.8) - [CVE-2020-35470](https://insights.sbomify.com/CVE-2020-35470/): Information disclosure in n/a (high 8.8) - [CVE-2024-23324](https://insights.sbomify.com/CVE-2024-23324/): Envoy ext auth can be bypassed when Proxy protocol filter sets invalid UTF-8 metadata (high 8.6) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-32778 and fix it if it is affected. What it is: CVE-2021-32778 is a medium-severity denial of service vulnerability in Envoyproxy Envoy, published on 24 Aug 2021. 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-2021-32778 in the wild and no public exploit code. Affected packages and fixed versions: - envoy (Bitnami): affected from 1.16.0; fixed in 1.16.5, 1.17.4, 1.18.4, 1.19.1 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-2021-32778/ (Markdown: https://insights.sbomify.com/CVE-2021-32778/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32778 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32778 - OSV: https://osv.dev/vulnerability/CVE-2021-32778 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-32778/ Summaries are generated and may contain mistakes; the official description above is the record.