CVE-2021-31439

Unauthenticated code execution via DSI length overflow

Published May 21, 2021 · Updated Aug 3, 2024

Heap-based buffer overflow in Netatalk on Synology DiskStation Manager before 6.2.3-25426-3 allows network-adjacent attackers to execute code. The dsi_stream_receive path fails to validate a user-supplied DSI data length before copying the data into a heap-based buffer. No authentication is required, but the attacker must reach the AFP service from an adjacent network; successful exploitation runs code in the Netatalk process.

CVSS severity8.8
High
EPSS probability2.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Netatalk on Synology DiskStation Manager before 6.2.3-25426-3 allows network-adjacent attackers to execute code. The dsi_stream_receive path fails to validate a user-supplied DSI data length before copying the data into a heap-based buffer. No authentication is required, but the attacker must reach the AFP service from an adjacent network; successful exploitation runs code in the Netatalk process.

The record

CVE
CVE-2021-31439
Published
May 21, 2021
Updated
Aug 3, 2024
Vendor
Synology
Product
DiskStation Manager
Classifications
CWE-122, CWE-787, T1210
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 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=6.1.1-15101-4

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Synology · DiskStation Managerversion=6.1.1-15101-4

Published CVSS scores

8.8Zero Day InitiativeCVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
5.8NIST NVDAV:A/AC:L/Au:N/C:P/I:P/A:P

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write
T1210Exploitation of Remote Services

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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