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CVE-2021-21299 — Vulnerability in hyper — CVE Details

HIGH

Multiple Transfer-Encoding headers misinterprets request payload

Published February 5, 2021Updated November 8, 2023Source: osv

Summary

hyper's 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".

Advisory Timeline

  • First published February 5, 2021 (2075 days ago).
  • Last revised November 8, 2023 — 1006 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Cargo
Update hyper to 0.12.36 or later
cargo update -p hyper --precise 0.12.36

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: crates.io (1).

PackageEcosystemAffectedFixed In
hyper
crates.io
All versions0.12.36, 0.13.10, 0.14.3

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 8.1 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Frequently Asked Questions

What is CVE-2021-21299?
Multiple Transfer-Encoding headers misinterprets request payload This vulnerability has been assigned a severity rating of HIGH (CVSS score: 8.1/10).
How do I check if my project is affected by CVE-2021-21299?
CVE-2021-21299 affects hyper. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2021-21299 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
8.1

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

RUSTSEC-2021-0020
GHSA-6hfq-h8hq-87mf

Related CVEs

  • CVE-2020-35863
    CRITICAL

    Flaw in hyper allows request smuggling by sending a body in GET requests

  • CVE-2021-32714
    CRITICAL

    Integer overflow in `hyper`'s parsing of the `Transfer-Encoding` header leads to data loss

  • CVE-2020-35863
    CRITICAL

    HTTP Request Smuggling in hyper

  • CVE-2026-93657
    HIGH

    hickory-resolver: Resolver::lookup() and Resolver::lookup_ip() APIs obscure DNSSEC validation failures

  • CVE-2026-18140
    HIGH

    aws-smithy-json: Uncontrolled recursion in the aws-smithy-json unknown-key skip path allows unauthenticated remote denial of service in smithy-rs generated servers

More crates.io advisories

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