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CVE-2021-39204

25
FAUCET Score

CVE-2021-39204 is a Denial of Service (DoS) vulnerability affecting Pomerium, an open-source identity-aware access proxy, and its underlying Envoy proxy. The vulnerability stems from Envoy's inefficient handling of HTTP/2 stream resets, leading to high CPU utilization when numerous streams are reset. This issue carries a CVSS score of 7.5 (HIGH), indicating it can be exploited remotely with low attack complexity, resulting in a complete loss of availability. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
<= 1.16.4CPE matchmatch criteria
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
>= 1.17.0, < 1.17.4CPE matchmatch criteria
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
>= 1.18.0, < 1.18.4CPE matchmatch criteria
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*
1.19.0CPE matchmatch criteria
cpe:2.3:a:envoyproxy:envoy:1.19.0:*:*:*:*:*:*:*
< 0.14.8CPE matchmatch criteria
cpe:2.3:a:pomerium:pomerium:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.66%
Probability of exploitation in next 30 days
EPSS Percentile
74.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0166 is in the 57th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

gopatch availablevia ghsa
Product: github.com/pomerium/pomeriumFixed in: 0.14.8
gopatch availablevia ghsa
Product: github.com/pomerium/pomeriumFixed in: 0.15.1

Vendor Advisories (1)

goGHSA-5wjf-62hw-q78rhigh

Excessive CPU usage

Sep 10, 2021

References

github.com / envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chcc
Third Party Advisory
github.com / pomerium/pomerium/security/advisories/GHSA-5wjf-62hw-q78r
Third Party Advisory
groups.google.com / g/envoy-announce/c/5xBpsEZZDfE/m/wD05NZBbAgAJ
Not Applicable