Security readout for executives and security teams
Plain-English summary
This flaw affects Rust services using vulnerable hyper HTTP/1 server code. It can let mismatched proxy and backend parsing create request smuggling conditions. The business risk is usually limited, but internet-facing services behind proxies should be checked because desync issues can bypass routing assumptions.
Executive priority
Treat this as a targeted remediation item, not an emergency. Prioritize externally reachable Rust services behind HTTP proxies, then address internal services during normal dependency maintenance.
Technical view
hyper versions before 0.14.10 accepted an illegal plus-prefixed Content-Length value. If an upstream proxy did not parse that header but still forwarded it, hyper could interpret the request differently, enabling HTTP request smuggling or desync behavior. The issue applies when built with rustc 1.5.0 or newer.
Likely exposure
Exposure is most likely in Rust applications using hyper before 0.14.10 as an HTTP/1 server, especially when deployed behind an upstream HTTP proxy. Direct exposure without a parsing mismatch is less clear from the sources.
Exploitation context
The source bundle does not show CISA KEV listing or cited active exploitation. Exploitation depends on a specific proxy-to-backend parsing mismatch, which raises practical complexity and limits broad urgency.
Researcher notes
This is a CWE-444 HTTP parsing inconsistency issue. The key condition is disagreement between the upstream proxy and hyper about an illegal Content-Length form. Evidence supports patch availability and workarounds, but not active exploitation.
Mitigation direction
- Upgrade hyper to version 0.14.10 or later.
- Reject requests with plus-prefixed Content-Length values before they reach hyper.
- Ensure upstream proxies reject or consistently handle such Content-Length headers.
- Check current vendor guidance for affected dependency branches.
Validation and detection
- Inventory Rust services and dependency lockfiles for hyper versions before 0.14.10.
- Confirm whether vulnerable services expose HTTP/1 server functionality.
- Identify deployments where hyper sits behind an upstream HTTP proxy.
- Verify proxy handling of malformed Content-Length values is consistent with backend behavior.
- Retest dependency versions after upgrade or rebuild.
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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CWE-444: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-32715 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
- Low
- CVSS
- 3.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N
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:R/S:U/C:L/I:N/A:N1.61.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
3.1LowVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/hyperium/hyper/security/advisories/GHSA-f3pg-qwvg-p99cCVE reference · x_refsource_CONFIRM
- https://github.com/rust-lang/rust/pull/28826/commits/123a83326fb95366e94a3be1a74775df4db97739CVE reference · x_refsource_MISC
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.