CVE-2021-3554Network attack vector

Patch-source redirection via unrestricted relay address

Published Nov 24, 2021 · Updated Sep 16, 2024

Improper access control in Bitdefender Endpoint Security Tools for Linux allows remote attackers to redirect relay patch downloads. The relay-role patchesUpdate API fails to restrict the remote address supplied for patch retrieval, causing downloads to use an attacker-selected location. Exploitation requires the endpoint to operate as a relay; public material does not describe whether downloaded patch content receives separate validation.

CVSS severity9.0
Critical
EPSS probability2.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Bitdefender Endpoint Security Tools for Linux allows remote attackers to redirect relay patch downloads. The relay-role patchesUpdate API fails to restrict the remote address supplied for patch retrieval, causing downloads to use an attacker-selected location. Exploitation requires the endpoint to operate as a relay; public material does not describe whether downloaded patch content receives separate validation.

The record

CVE
CVE-2021-3554
Published
Nov 24, 2021
Updated
Sep 16, 2024
Vendor
Bitdefender
Product
GravityZone
Classifications
CWE-284, T1195.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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?

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

  1. Affected versionversion=unspecified <6.24.1-1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Bitdefender · GravityZoneversion=unspecified <6.24.1-1
Bitdefender · Bitdefender Endpoint Security Tools for Linuxversion=unspecified <6.6.27.390; version=unspecified <7.1.2.33

Published CVSS scores

9.0BitdefenderCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
10.0NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1195.002Compromise Software Supply Chain

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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Your stack

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