Security readout for executives and security teams
Plain-English summary
This flaw affects NTFS-3G before 2021.8.22 when it handles a specially crafted NTFS image. Successful exploitation could corrupt memory and affect confidentiality, integrity, and availability. The source bundle does not show internet-facing exposure or confirmed active exploitation.
Executive priority
Treat this as a moderate operational risk. Prioritize shared workstations, forensic systems, backup tooling, and servers that handle external media or disk images. Routine patching is usually sufficient unless the environment processes untrusted NTFS content at scale.
Technical view
CVE-2021-39256 is a heap-based buffer overflow in ntfs_inode_lookup_by_name in NTFS-3G before 2021.8.22. The CVSS vector is local, low complexity, high privileges required, no user interaction, unchanged scope, with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most likely on Linux or Unix systems using NTFS-3G to mount or inspect NTFS filesystems, especially removable media, disk images, forensic workflows, or automation that processes untrusted NTFS content.
Exploitation context
The provided CVSS data requires local access and high privileges. A crafted NTFS image is required. CISA KEV status is false, and the supplied sources do not document active exploitation.
Researcher notes
The bundle identifies the vulnerable function and version boundary but does not include exploit details, fixed commits, or detailed affected distribution versions. Validate through vendor advisories and package metadata rather than relying only on upstream version strings.
Mitigation direction
- Upgrade NTFS-3G to 2021.8.22 or later where available.
- Apply Debian, Debian LTS, Gentoo, or other vendor security updates.
- Limit privileged mounting or processing of untrusted NTFS images.
- Review automount and image-processing workflows for unnecessary NTFS handling.
- Check vendor guidance if package backport versions differ from upstream numbering.
Validation and detection
- Inventory systems with NTFS-3G installed or bundled.
- Confirm installed packages include the CVE-2021-39256 fix.
- Identify workflows that mount removable NTFS media or disk images.
- Prioritize hosts where privileged services process untrusted NTFS content.
- Review distro advisories for fixed package versions and backport notes.
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-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-39256 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
- [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.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.