CVE-2021-32778
Excessive CPU utilization when closing HTTP/2 streams
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.
How to fix CVE-2021-32778
To remediate CVE-2021-32778, upgrade the affected package to a fixed version below.
- —upgrade to 1.16.5 or later
Is CVE-2021-32778 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 1.16.0, < 1.16.5, >= 1.17.0, < 1.17.4, >= 1.18.0, < 1.18.4, >= 1.19.0, < 1.19.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |