CVE-2021-32778

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    CVE-2021-32778

    Published: 24 Aug 2021Last Modified: 7 Aug 2026

    Summary:

    Details: 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.

    References: https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chcc, https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_history

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 8fb3cb86082b17144a80402f5367ae65f06083bd
    Fixed -72ec3eed50b4154cb6d2251667b4c1c1ddfaa266

    Affected versions

    1.19.0

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2021-32778 | CVE-DB