CVE-2020-25583Public exploit

Adjacent code execution via DNSSL label overflow

Published Mar 29, 2021 · Updated Aug 4, 2024

Buffer overflow in FreeBSD rtsold allows physically proximate attackers to execute code via a crafted DNSSL router advertisement. The dname_labeldec function copies each decoded label into a 1,025-byte stack buffer while checking only the bytes already written, not whether the next label fits. Exploitation requires rtsold to be running on the same physical link; its FreeBSD 12.2 Capsicum sandbox limits the compromised process.

CVSS severity9.8
Critical
EPSS probability1.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer overflow in FreeBSD rtsold allows physically proximate attackers to execute code via a crafted DNSSL router advertisement. The dname_labeldec function copies each decoded label into a 1,025-byte stack buffer while checking only the bytes already written, not whether the next label fits. Exploitation requires rtsold to be running on the same physical link; its FreeBSD 12.2 Capsicum sandbox limits the compromised process.

The record

CVE
CVE-2020-25583
Published
Mar 29, 2021
Updated
Aug 4, 2024
Vendor
The FreeBSD Project
Product
FreeBSD
Classifications
CWE-120
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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 12.2-RELEASE before p1, 12.1-RELEASE before p11, 11.4-RELEASE before p5

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

The FreeBSD Project · FreeBSDversion=FreeBSD 12.2-RELEASE before p1, 12.1-RELEASE before p11, 11.4-RELEASE before p5

Published CVSS scores

10.0NIST NVDAV:N/AC:L/Au:N/C:C/I:C/A:C
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Public exploit references

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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