8.1

CVE-2021-21299: hyper HTTP Request/Response Smuggling

CVSS: 8.1v3.1HighModified
AliasesUBUNTU-CVE-2021-21299DEBIAN-CVE-2021-21299openSUSE-SU-2024:12238-1
Published 11-02-2021Last modified 03-08-2024
Open JSON

Vulnerability summary

CVE-2021-21299 is a high (CVSS 8.1) HTTP Request/Response Smuggling vulnerability in hyper. EPSS estimates a 4.73% chance of exploitation in the next 30 days, higher than 91.7% of scored vulnerabilities.

Overall risk
33/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.1/10
010
High · v3.1 (NVD)
EPSS score
4.73%
0%100%
Low · -0.04 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Duplicates 1
CVE-2021-26959

Timeline

  1. 11-02-2021
    PublishedVulnerability first disclosed.
  2. 03-08-2024
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

6 scores · 5 sources · 2 versions

EPSS trend

Probability

4.73%

Chance of exploitation in the next 30 days

Percentile

92%

Versus all other CVEs

30-day change

-0.04 pp

From 4.77% on 20-09-2026

20-09-202620-10-2026
EPSS score
4.73%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Opensuse3 products
  • spotifyd&distro=openSUSE Tumbleweed< 0.3.3-9.1
  • tuigreet&distro=openSUSE Tumbleweed< 0.7.1-6.1
  • wayshot&distro=openSUSE Tumbleweed< 1.1.9-1.1
Crates.Io1 product
  • hyper≥ 0.14.0, < 0.14.3 | ≥ 0.13.0, < 0.13.10 | ≥ 0.12.0, < 0.12.36 | ≥ 0.14.0-0, < 0.14.3
Debian1 product
  • rust-hyper< 0.14.19-1
Hyper1 product
  • hyper≥ 0.12.0, < 0.13.10 | ≥ 0.14.0, < 0.14.3
Hyperium1 product
  • hyper< 0.13.10 | ≥ 0.14.0, < 0.14.3
Ubuntu1 product
  • rust-hyperAll versions (No fix recorded)

6 vendors · 8 products

References

11 links
Show all 11 references