CVE-2021-39257

A crafted NTFS image with an unallocated bitmap can lead to a endless recursive function call chain (starting from ntfs_attr_pwrite), causing stack consumption in NTFS-3G < 2021.8.22.

Published: 2021-09-07 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-39257 is rated Low Risk (32.3/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.37%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-39257

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.16% 0.37% +0.21%
2 2026-03-31 0.15% 0.16% +0.01%
3 2026-02-25 — 0.15% —

Full EPSS history (16 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-39257

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]
4.7 2.0 MEDIUM
AV:L/AC:M/Au:N/C:N/I:N/A:C Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 3.4 6.9 [email protected]

Weakness enumeration for CVE-2021-39257

OS Trackers for CVE-2021-39257

vendor priority summary link
alpine medium CVE-2021-39257: 1 source package rows (ntfs-3g); 8 state rows across 7 repos (3.11-main, 3.12-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 8. https://security.alpinelinux.org/vuln/CVE-2021-39257
debian not yet assigned CVE-2021-39257 not yet assigned priority: Debian including 1 source packages (ntfs-3g), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-39257
gentoo high CVE-2021-39257: 1 GLSA(s) (202301-01), 1 atom(s) (sys-fs/ntfs3g); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-39257
redhat medium — https://access.redhat.com/security/cve/CVE-2021-39257
ubuntu medium CVE-2021-39257 medium priority: Ubuntu including 1 source packages (ntfs-3g), 8 status rows across 8 suites (bionic, focal, hirsute, impish, jammy, trusty, upstream, xenial): released 7, needs-triage 1. https://ubuntu.com/security/CVE-2021-39257

Affected software / configurations for CVE-2021-39257

Vendor Product Version Raw CPE
tuxera ntfs-3g < 2021.8.22 cpe:2.3:a:tuxera:ntfs-3g:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

References for CVE-2021-39257

cvelogic Threat Intelligence