CVE-2021-32778
MEDIUMDescription
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
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
Exploit Intelligence
Moderate risk: more likely to be exploited than 66% of all known CVEs.
References
Related Vulnerabilities
Other CWE-834 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-35515 | High | 7.5 | 12% | - | Fix |
| CVE-2021-39924 | High | 7.5 | 4.9% | - | Fix |
| CVE-2023-1993 | Medium | 6.3 | 4.1% | - | Fix |
| CVE-2018-14342 | High | 7.5 | 3.7% | - | Fix |
| CVE-2020-14303 | High | 7.5 | 3.5% | - | Fix |
| CVE-2018-9133 | Medium | 6.5 | 3.2% | - | Fix |
Common questions
How do I fix CVE-2021-32778?
Upgrade envoy to 1.18.4 or later.
Is CVE-2021-32778 being actively exploited?
Not that we know of. CVE-2021-32778 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 66% of all scored CVEs.
How severe is CVE-2021-32778?
CVE-2021-32778 has a CVSS v3 base score of 5.8, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-32778 affect?
Published advisories record a fix for envoy (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.