CVE-2021-29629Network attack vector

Service interruption via malformed RADIUS attributes

Published May 28, 2021 · Updated Aug 3, 2024

Improper message validation in affected FreeBSD releases allows remote attackers to crash or hang applications that process RADIUS messages. rad_get_attr subtracts the Type and Length header size before validating an attribute length, while is_valid_response accepts a zero-length attribute and can loop forever. The issue is reachable only when a libradius consumer processes an untrusted RADIUS message; affected servers trust malicious clients, and affected clients trust malicious servers.

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

What happened

Improper message validation in affected FreeBSD releases allows remote attackers to crash or hang applications that process RADIUS messages. rad_get_attr subtracts the Type and Length header size before validating an attribute length, while is_valid_response accepts a zero-length attribute and can loop forever. The issue is reachable only when a libradius consumer processes an untrusted RADIUS message; affected servers trust malicious clients, and affected clients trust malicious servers.

The record

CVE
CVE-2021-29629
Published
May 28, 2021
Updated
Aug 3, 2024
Vendor
The FreeBSD Project
Product
FreeBSD
Classifications
CWE-20, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 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?

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

  1. Affected versionversion=FreeBSD 13.0-RELEASE before p1, 12.2-RELEASE before p7, 11.4-RELEASE before p10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The FreeBSD Project · FreeBSDversion=FreeBSD 13.0-RELEASE before p1, 12.2-RELEASE before p7, 11.4-RELEASE before p10

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST National Vulnerability DatabaseCVSS: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.

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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-20Improper Input Validation
T1499Endpoint Denial of Service

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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