Security readout for executives and security teams
Plain-English summary
CVE-2021-39253 affects NTFS-3G before 2021.8.22. A malicious NTFS filesystem image can trigger an out-of-bounds read. Business risk is most relevant where users, automation, or forensic workflows mount or inspect untrusted NTFS media or images.
Executive priority
Treat this as a targeted operational hygiene issue, not an internet-wide emergency. Prioritize patching systems that process untrusted storage media, forensic images, or customer-supplied filesystems, because those are the realistic exposure points.
Technical view
The flaw is an out-of-bounds read in ntfs_runlists_merge_i when processing a crafted NTFS image. The CVSS 3.1 score is 6.7 with local attack vector, low complexity, high privileges, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is likely on Linux or Unix-like systems using NTFS-3G versions earlier than 2021.8.22, especially endpoints, file-ingest services, forensic workstations, or storage tools that handle untrusted NTFS volumes.
Exploitation context
The source bundle does not indicate active exploitation, and KEV is false. Exploitation requires local access with high privileges according to the CVSS vector, plus a crafted NTFS image processed by vulnerable NTFS-3G code.
Researcher notes
Key evidence is concise: crafted NTFS image, ntfs_runlists_merge_i, NTFS-3G before 2021.8.22, CWE-125 and CWE-20. Sources do not provide exploit steps or active exploitation evidence. Avoid expanding impact beyond the CVSS vector and vendor advisories.
Mitigation direction
- Upgrade NTFS-3G to 2021.8.22 or a vendor-fixed package.
- Apply relevant Debian, Fedora, Gentoo, or distribution security updates.
- Limit mounting or inspection of untrusted NTFS images on vulnerable systems.
- Restrict privileged access to workflows that process removable media or disk images.
- Check current vendor guidance for package-specific fixed versions.
Validation and detection
- Inventory installed NTFS-3G versions across Linux and Unix-like systems.
- Identify systems that mount removable NTFS media or process NTFS disk images.
- Confirm package versions against distribution security advisories.
- Review privileged workflows that accept externally supplied filesystem images.
- Document any compensating controls for untrusted media handling.
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-125: 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 lookupCWE-20: 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 lookupCVE-2021-39253 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
- Medium
- CVSS
- 6.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:H/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:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H0.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.7MediumVector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/tuxera/ntfs-3g/releasesCVE reference
- https://github.com/tuxera/ntfs-3g/security/advisories/GHSA-q759-8j5v-q5jpCVE reference
- DSA-4971CVE reference · vendor-advisory
- FEDORA-2021-e7c8ba6301CVE reference · vendor-advisory
- FEDORA-2021-5b1dac797bCVE reference · vendor-advisory
- [debian-lts-announce] 20211116 [SECURITY] [DLA 2819-1] ntfs-3g security updateCVE reference · mailing-list
- GLSA-202301-01CVE 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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.