Security readout for executives and security teams
Plain-English summary
This Envoy flaw can crash affected proxy deployments when specially crafted traffic reaches configurations using body-expanding filters. The business impact is availability loss, not data theft, but Envoy often sits on critical service paths, so outages can cascade across APIs or service meshes.
Executive priority
Prioritize remediation for internet-facing or cross-boundary Envoy deployments because the flaw can disrupt critical traffic paths without authentication. Internal deployments using the named filters should also be scheduled promptly, especially where service reliability is business-critical.
Technical view
Envoy could continue request or response processing after a locally generated response caused by internal buffer overflow in the filter chain. With extensions that modify and increase body size, this can access freed memory and cause denial of service. Fixed releases are 1.19.1, 1.18.4, 1.17.4, and 1.16.5.
Likely exposure
Exposure is likely where Envoy versions 1.16.0-1.16.4, 1.17.0-1.17.3, 1.18.0-1.18.3, or 1.19.0 handle untrusted downstream or upstream traffic and use decompressor, json-transcoder, grpc-web, or similar body-modifying extensions.
Exploitation context
The supplied sources do not report active exploitation, and this CVE is not marked KEV. The advisory describes a specifically constructed request from an untrusted downstream or upstream peer causing denial of service under vulnerable filter conditions.
Researcher notes
The trigger depends on vulnerable Envoy versions plus extensions that increase request or response body size. Evidence supports denial of service through use-after-free after incomplete processing termination. Sources do not support claims of confidentiality impact, integrity impact, or in-the-wild exploitation.
Mitigation direction
- Upgrade Envoy to 1.19.1, 1.18.4, 1.17.4, 1.16.5, or later fixed branches.
- Disable Envoy decompressor, json-transcoder, grpc-web, or similar body-expanding extensions if feasible.
- Review proprietary Envoy extensions that modify and increase request or response body sizes.
- Check the Envoy advisory and version history before applying compensating controls.
Validation and detection
- Inventory Envoy versions across edge proxies, gateways, and service-mesh sidecars.
- Inspect Envoy configurations for decompressor, json-transcoder, grpc-web, or proprietary body-modifying filters.
- Confirm whether affected Envoy instances receive traffic from untrusted downstream or upstream peers.
- Verify deployed versions include the listed fixed releases or equivalent vendor-provided fixes.
- Review availability monitoring for unexplained Envoy crashes or restarts in exposed paths.
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-416: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-32781 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.6HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.envoyproxy.io/docs/envoy/v1.19.0/version_history/version_historyCVE reference · x_refsource_MISC
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-5vhv-gp9v-42qvCVE 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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.