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TI-2021-04399 Aliases CVE-2021-21299GHSA-6hfq-h8hq-87mf

Multiple Transfer-Encoding headers misinterprets request payload

Priority MEDIUM 43CWE-444Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub.

Summary

hyper is an open-source HTTP library for Rust (crates.io). In hyper from version 0.12.0 and before versions 0.13.10 and 0.14.3 there is a vulnerability that can enable a request smuggling attack. The HTTP server code had a flaw that incorrectly understands some requests with multiple transfer-encoding headers to have a chunked payload, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that understands the request payload boundary differently can result in "request smuggling" or "desync attacks". To determine if vulnerable, all these things must be true: 1) Using hyper as an HTTP server (the client is not affected), 2) Using HTTP/1.1 (HTTP/2 does not use transfer-encoding), 3) Using a vulnerable HTTP proxy upstream to hyper. If an upstream proxy correctly rejects the illegal transfer-encoding headers, the desync attack cannot succeed. If there is no proxy upstream of hyper, hyper cannot start the desync attack, as the client will repair the headers before forwarding. This is fixed in versions 0.14.3 and 0.13.10. As a workaround one can take the following options: 1) Reject requests that contain a `transfer-encoding` header, 2) Ensure any upstream proxy handles `transfer-encoding` correctly.

Why it matters now

EPSS 0.04789 91st percentileScored 2026-11-07
Fix Fixed hyper (hyperium): 0.13.10, 0.14.3hyper (crates.io): 0.14.3, 0.13.10, 0.12.36

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
hyperiumhyperbefore 0.13.10; 0.14.0 to before 0.14.30.13.10, 0.14.3Patch availableCNA
—hyper (crates.io)0.14.0 to before 0.14.30.14.3Patch availableGHSA-6hfq-h8hq-87mf
—hyper (crates.io)0.13.0 to before 0.13.100.13.10Patch availableGHSA-6hfq-h8hq-87mf
—hyper (crates.io)0.12.0 to before 0.12.360.12.36Patch availableGHSA-6hfq-h8hq-87mf
  • hyper Vendorhyperium Affected before 0.13.10; 0.14.0 to before 0.14.3 Fixed in 0.13.10, 0.14.3 Patch available CNA
  • hyper (crates.io) Vendor— Affected 0.14.0 to before 0.14.3 Fixed in 0.14.3 Patch available GHSA-6hfq-h8hq-87mf
  • hyper (crates.io) Vendor— Affected 0.13.0 to before 0.13.10 Fixed in 0.13.10 Patch available GHSA-6hfq-h8hq-87mf
  • hyper (crates.io) Vendor— Affected 0.12.0 to before 0.12.36 Fixed in 0.12.36 Patch available GHSA-6hfq-h8hq-87mf

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:hyper:hyper:*:*:*:*:*:rust:*:*0.12.0 to before 0.13.10; 0.14.0 to before 0.14.3Vulnerablehyperium
  • cpe:2.3:a:hyper:hyper:*:*:*:*:*:rust:*:* Versions 0.12.0 to before 0.13.10; 0.14.0 to before 0.14.3 Vulnerable ·hyperium

Remediation

  • Fix · CNA hyper (hyperium) Fixed in 0.13.10, 0.14.3
  • Fix · GHSA-6hfq-h8hq-87mf hyper (crates.io) Fixed in 0.14.3 Advisory →
  • Fix · GHSA-6hfq-h8hq-87mf hyper (crates.io) Fixed in 0.13.10 Advisory →
  • Fix · GHSA-6hfq-h8hq-87mf hyper (crates.io) Fixed in 0.12.36 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-21299
  2. 2026-10-03 Alias added: GHSA-6hfq-h8hq-87mf

References

Patch 1

Advisory 5

Other 1

  • TI-2023-11846 An issue was discovered in hyper v0.13.7. CVSS 3.1HIGH 7.5
  • TI-2022-13369 Hyperium Hyper before 0.14.19 does not allow for customization of the… CVSS 3.1HIGH 7.5
  • TI-2020-18306 An issue was discovered in the hyper crate before 0.12.34 for Rust. CVSS 3.1CRITICAL 9.8
  • TI-2021-12382 Integer Overflow in Chunked Transfer-Encoding CVSS 3.1CRITICAL 9.1
  • TI-2021-12383 Lenient Parsing of Content-Length Header When Prefixed with Plus Sign CVSS 3.1MEDIUM 5.3
  • TI-2017-13760 An issue was discovered in the hyper crate before 0.9.18 for Rust. CVSS 3.0MEDIUM 5.3
See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences