Security readout for executives and security teams
Plain-English summary
This flaw can let an unauthenticated network user make vulnerable Pomerium deployments spend excessive CPU handling HTTP/2 stream resets. The business impact is service disruption, not data theft or tampering. Public sources name patched Pomerium releases 0.14.8 and 0.15.1.
Executive priority
Treat this as a high-priority availability risk for Pomerium-protected services. It does not indicate data compromise, but outage potential is meaningful because exploitation requires no authentication and can target network-reachable proxies.
Technical view
Pomerium inherited an Envoy HTTP/2 stream reset handling issue with excessive computational complexity. Many stream resets can drive high CPU utilization and cause denial of service. Affected Pomerium versions are before 0.14.8 and 0.15.0 before 0.15.1. CVSS 3.1 is 7.5, network exploitable, no privileges or user interaction required.
Likely exposure
Exposure is most likely where Pomerium is deployed as an identity-aware access proxy and reachable over the network, especially internet-facing gateways. Only the affected version ranges are supported by the provided evidence.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. The CVSS vector indicates low-complexity unauthenticated network abuse against availability, but sources here do not provide exploit prevalence or weaponization status.
Researcher notes
The evidence ties Pomerium exposure to Envoy’s HTTP/2 reset complexity issue. The provided sources identify affected Pomerium ranges and patched Pomerium releases, but do not provide proof of active exploitation, indicators, or compensating controls beyond upgrading/checking advisories.
Mitigation direction
- Upgrade affected Pomerium deployments to 0.14.8, 0.15.1, or later supported releases.
- Prioritize internet-facing and business-critical Pomerium gateways first.
- Check Pomerium and Envoy advisories for any environment-specific operational guidance.
- Monitor CPU and availability during and after remediation.
Validation and detection
- Inventory Pomerium versions across production, staging, and edge environments.
- Flag versions before 0.14.8 and 0.15.0 before 0.15.1 as affected.
- Confirm upgraded deployments report a patched Pomerium release.
- Review metrics for unusual CPU spikes on Pomerium gateways.
- Validate critical protected applications remain reachable after upgrade.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Open ATT&CK lookupCVE-2021-39204 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://groups.google.com/g/envoy-announce/c/5xBpsEZZDfE/m/wD05NZBbAgAJCVE reference · x_refsource_MISC
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-3xh3-33v5-chccCVE reference · x_refsource_MISC
- https://github.com/pomerium/pomerium/security/advisories/GHSA-5wjf-62hw-q78rCVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Excessive Iteration
Excessive Iteration represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.