Security readout for executives and security teams
Plain-English summary
CVE-2021-31439 is a high-severity flaw in Synology DiskStation Manager’s Netatalk handling. A nearby network attacker could exploit it without logging in to run code in the affected process, threatening NAS confidentiality, integrity, and availability.
Executive priority
Prioritize remediation for NAS devices on shared or less-trusted networks. The issue is high impact because no authentication is required, but urgency should be based on actual DSM version and reachable service exposure.
Technical view
The flaw is a heap-based buffer overflow in Netatalk DSI structure processing caused by insufficient validation of user-supplied length before copying data. The source bundle identifies Synology DiskStation Manager 6.1.1-15101-4 as affected and gives CVSS 8.8 with adjacent-network, unauthenticated exploitation.
Likely exposure
Exposure is most likely where affected Synology DSM systems have vulnerable Netatalk processing reachable from local, wireless, VPN, or bridged network segments. The bundle does not prove broader product or version impact beyond the listed DSM version.
Exploitation context
The sources support unauthenticated network-adjacent code execution, but the bundle marks CISA KEV as false and provides no cited evidence of active exploitation. Treat this as credible pre-auth RCE risk, not confirmed in-the-wild exploitation.
Researcher notes
Evidence ties the vulnerability to ZDI-CAN-12326 and CWE-122. Public bundle data supports root-cause classification and attack vector, but does not include exploit details, exact fixed Synology versions, or active exploitation proof.
Mitigation direction
- Review Synology advisory Synology_SA_20_26 for affected and fixed DSM releases.
- Apply Synology-provided DSM updates for impacted NAS devices.
- Restrict access to Netatalk-related services to trusted networks only.
- Disable unnecessary Netatalk or file-sharing services where operationally feasible.
- For Linux Netatalk deployments, review Debian and Gentoo advisories and update packages.
Validation and detection
- Inventory Synology DSM devices and record exact DSM versions.
- Identify systems running DSM 6.1.1-15101-4 or advisory-listed affected releases.
- Check whether Netatalk-related services are enabled and reachable from adjacent networks.
- Confirm vendor updates are installed after remediation.
- Review network controls limiting untrusted local, wireless, and VPN access.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-122: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-31439 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.8HighVector: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.zerodayinitiative.com/advisories/ZDI-21-492/CVE reference
- https://www.synology.com/zh-hk/security/advisory/Synology_SA_20_26CVE reference
- [debian-lts-announce] 20230516 [SECURITY] [DLA 3426-1] netatalk security updateCVE reference · mailing-list
- DSA-5503CVE reference · vendor-advisory
- GLSA-202311-02CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Heap-based Buffer Overflow
Heap-based Buffer Overflow represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.