CVE-2021-32714Public exploitNetwork attack vector

Data truncation via overflowing HTTP chunk size

Published Jul 7, 2021 · Updated Aug 3, 2024

Integer overflow in Hyperium Hyper before 0.14.10 allows remote attackers to truncate HTTP/1 message bodies via oversized chunk sizes. The HTTP/1 decoder in src/proto/h1/decode.rs multiplied and added hexadecimal chunk-size digits into a u64 without checked arithmetic, causing oversized values to wrap. Reachability requires HTTP/1 client or server use and a chunk exceeding 64 bits; request desynchronization additionally requires an upstream proxy that accepts the larger value.

CVSS severity5.9
Medium
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Integer overflow in Hyperium Hyper before 0.14.10 allows remote attackers to truncate HTTP/1 message bodies via oversized chunk sizes. The HTTP/1 decoder in src/proto/h1/decode.rs multiplied and added hexadecimal chunk-size digits into a u64 without checked arithmetic, causing oversized values to wrap. Reachability requires HTTP/1 client or server use and a chunk exceeding 64 bits; request desynchronization additionally requires an upstream proxy that accepts the larger value.

The record

CVE
CVE-2021-32714
Published
Jul 7, 2021
Updated
Aug 3, 2024
Vendor
Hyperium
Product
Hyper
Classifications
CWE-190, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.14.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hyperium · Hyperversion=< 0.14.10

Published CVSS scores

5.9GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
9.1RustSecCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo