Security readout for executives and security teams
Plain-English summary
A malicious NTFS disk image could make vulnerable NTFS-3G mishandle filesystem metadata. Because NTFS-3G often runs with elevated privileges when mounting disks, this matters most for systems that mount untrusted Windows-formatted media or images. The provided sources do not show active exploitation.
Executive priority
Prioritize remediation on systems that handle untrusted storage, forensic images, shared lab media, or user-uploaded disk images. General server urgency is lower unless those workflows exist, but patching is still appropriate because the vulnerable parser may run with elevated privileges.
Technical view
CVE-2021-39255 is an out-of-bounds read in NTFS-3G before 2021.8.22, caused by invalid attribute handling in ntfs_attr_find_in_attrdef. The CVSS vector is local, low complexity, high privileges required, and no user interaction. Reported impacts are high confidentiality, integrity, and availability.
Likely exposure
Exposure is likely where NTFS-3G versions older than 2021.8.22 are installed and used to mount or process NTFS filesystems from removable media, disk images, forensic workflows, or user-supplied storage.
Exploitation context
The bundle describes a crafted NTFS image trigger, not remote exploitation. KEV is false, and the supplied references do not claim active exploitation. Practical risk depends on whether vulnerable hosts process untrusted NTFS media or images in privileged contexts.
Researcher notes
The issue is tied to CWE-20 input validation and invalid NTFS attribute parsing. The source bundle does not provide exploit details, proof of exploitation, or a universal mitigation beyond upgrading or applying vendor updates. Validate distro backports rather than relying only on upstream version strings.
Mitigation direction
- Upgrade NTFS-3G to 2021.8.22 or a vendor-fixed package.
- Apply relevant Debian, Debian LTS, or Gentoo security updates where applicable.
- Avoid mounting untrusted NTFS media or disk images on vulnerable systems.
- Check operating-system vendor guidance for backported fixed package versions.
Validation and detection
- Inventory hosts with NTFS-3G installed and record package versions.
- Confirm installed versions are 2021.8.22 or vendor-marked fixed builds.
- Identify workflows that mount removable NTFS media or user-supplied disk images.
- Review distro advisories for environment-specific package names and fixed versions.
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-2021-39255 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.