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CVE

CVE-2021-32778

Envoy is an open source L7 proxy and communication bus designed for large modern service oriented architectures. In affe

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.

MEDIUM · CVSS 5.8 EPSS 0.0006
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-834Excessive Iteration
CWE-834Excessive Iteration
▤

Affected Products & Versions

4
envoyproxy envoy>= 1.16.0 and < 1.16.5
envoyproxy envoy>= 1.17.0 and < 1.17.4
envoyproxy envoy>= 1.18.0 and < 1.18.4
envoyproxy envoyall versions
▣

Scoring & Timeline

5.8
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD24 Aug 2021 · 09:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
⚑

Vendor Advisories

1
rhsaRHEA-2021:4051Important
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
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 NotesVendor Advisory
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