Security readout for executives and security teams
Plain-English summary
CVE-2021-39214 affects mitmproxy versions before 7.0.3. A malicious client or server could hide HTTP traffic inside another message, causing security logic in mitmproxy hooks to miss it. The vendor says action is only required when mitmproxy protects an HTTP/1 service.
Executive priority
Treat as high priority only where mitmproxy is part of an HTTP/1 protection path. For development-only use, urgency is lower, but upgrading remains the clean remediation.
Technical view
mitmproxy 7.0.2 and earlier lack protection against HTTP request smuggling. Smuggled requests or responses can be captured as message body content, but not shown in the request list or processed through normal event hooks, bypassing custom access-control or sanitization logic.
Likely exposure
Exposure is most likely in environments using mitmproxy below 7.0.3 as a protective proxy for HTTP/1 services, especially with custom security checks in event hooks. Routine intercepting-proxy or development use may have limited business impact.
Exploitation context
The source bundle does not show KEV listing or confirmed active exploitation. The CVSS vector indicates network reachability, no privileges, no user interaction, high complexity, and potentially high confidentiality, integrity, and availability impact.
Researcher notes
The key security impact is hook bypass visibility, not just malformed traffic handling. Validate exposure by mapping mitmproxy’s role and version, then reviewing whether hidden messages could bypass locally implemented security decisions.
Mitigation direction
- Upgrade mitmproxy to version 7.0.3 or later.
- Inventory deployments running mitmproxy 7.0.2 or earlier.
- Prioritize systems where mitmproxy protects HTTP/1 services.
- Review vendor guidance before relying on compensating controls.
- Avoid treating vulnerable mitmproxy hooks as a security boundary.
Validation and detection
- Confirm installed mitmproxy versions are 7.0.3 or newer.
- Identify whether mitmproxy fronts any HTTP/1 services.
- Review custom event hooks for access-control or sanitization logic.
- Check deployment documentation for mitmproxy security-boundary assumptions.
- Confirm remediation through package or container version records.
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-2021-39214 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/mitmproxy/mitmproxy/security/advisories/GHSA-22gh-3r9q-xf38CVE 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.
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.