7.5

CVE-2021-32778: envoyproxy envoy Excessive Iteration

CVSS: 7.5v3.1HighModified
AliasesRHEA-2021:4051
Published 24-08-2021Last modified 03-08-2024
Open JSON

Vulnerability summary

CVE-2021-32778 is a high (CVSS 7.5) Excessive Iteration vulnerability in envoyproxy envoy. EPSS estimates a 1.23% chance of exploitation in the next 30 days, higher than 68.4% of scored vulnerabilities.

Overall risk
30/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
1.23%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 24-08-2021
    PublishedVulnerability first disclosed.
  2. 03-08-2024
    Last modifiedVulnerability information updated.

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 metrics

4 scores · 3 sources · 2 versions

EPSS trend

Probability

1.23%

Chance of exploitation in the next 30 days

Percentile

68%

Versus all other CVEs

30-day change

0.00 pp

From 1.23% on 19-09-2026

19-09-202619-10-2026
EPSS score
1.23%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Redhat13 products
  • servicemesh< 0:2.1.0-5.el8
  • servicemesh-cni< 0:2.1.0-5.el8
  • servicemesh-grafana< 0:7.2.1-2.el8
  • servicemesh-grafana-debuginfo< 0:7.2.1-2.el8
  • servicemesh-operator< 0:2.1.0-4.el8
Envoyproxy1 product
  • envoyEOL≥ 1.19.0, < 1.19.1 | ≥ 1.16.0, < 1.16.5 | ≥ 1.17.0, < 1.17.4 | ≥ 1.18.0, < 1.18.4 | 1.19.0

2 vendors · 14 products

References

10 links