HOMEVULNERABILITIESCVE-2021-28484
HIGH

CVE-2021-28484

CWE-835Published: April 14, 2021· Updated: Jun 17, 2026

7.5
CVSS v3.1

Official Description

An issue was discovered in the /api/connector endpoint handler in Yubico yubihsm-connector before 3.0.1 (in YubiHSM SDK before 2021.04). The handler did not validate the length of the request, which can lead to a state where yubihsm-connector becomes stuck in a loop waiting for the YubiHSM to send it data, preventing any further operations until the yubihsm-connector is restarted. An attacker can send 0, 1, or 2 bytes to trigger this.

NVD Source

Technical Analysis

CVE-2021-28484 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 7.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

Fedora1 product(s)
fedora
yubico1 product(s)
yubihsm connector
Source: NVD CPE · 2 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://github.com/Yubico/yubihsm-connector/releases
ADVISORYhttps://www.yubico.com/support/security-advisories/ysa-2021-02/
ADVISORYhttps://github.com/Yubico/yubihsm-connector/releases
ADVISORYhttps://www.yubico.com/support/security-advisories/ysa-2021-02/

All References (6)

→
https://github.com/Yubico/yubihsm-connector/releasesThird Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B7Q2KGXSPQEEONAWMFZRVH2TXWX3QPCQ/
→
https://www.yubico.com/support/security-advisories/ysa-2021-02/Vendor Advisory
→
https://github.com/Yubico/yubihsm-connector/releasesThird Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/B7Q2KGXSPQEEONAWMFZRVH2TXWX3QPCQ/
→
https://www.yubico.com/support/security-advisories/ysa-2021-02/Vendor Advisory

Quick Facts

CVE IDCVE-2021-28484
CVSS Score7.5 / 10
SeverityHIGH
WeaknessCWE-835
CISA KEVNo
Affected2 vendor(s)
PublishedApr 14, 2021

Related CVEs (CWE-835)

CVE-2026-24816
10.0
CVE-2018-20784
9.8
CVE-2017-12990
9.8
CVE-2017-12995
9.8
CVE-2017-12997
9.8
CVE-2026-24804
9.2

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-28484 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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