CVE-2021-32778
Deployments are susceptible to Denial of Service when Envoy is configured with high limit on H/2 concurrent streams.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.23%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 1.23% probability · 67th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-834
- Affected
- envoyproxy/envoy
- Source
- security-advisories@github.com
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chccThird Party Advisory
- https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_historyRelease Notes, Vendor Advisory
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chccThird Party Advisory
- https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_historyRelease Notes, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.