CVE-2021-28484Network attack vector

Service hang via undersized connector request

Published Apr 14, 2021 · Updated Aug 3, 2024

Denial of service in Yubico yubihsm-connector before 3.0.1 allows remote attackers to halt connector operations with a short HTTP request. The /api/connector handler forwards a 0- to 2-byte body to the YubiHSM, then holds its command lock indefinitely because the device sends no response. Remote reachability requires a non-default network listener; the default localhost binding limits triggering to local users, and service resumes only after restart.

CVSS severity7.5
High
EPSS probability1.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Yubico yubihsm-connector before 3.0.1 allows remote attackers to halt connector operations with a short HTTP request. The /api/connector handler forwards a 0- to 2-byte body to the YubiHSM, then holds its command lock indefinitely because the device sends no response. Remote reachability requires a non-default network listener; the default localhost binding limits triggering to local users, and service resumes only after restart.

The record

CVE
CVE-2021-28484
Published
Apr 14, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 14, 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

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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