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Fencer Vulns
medium 6.5

CVE-2021-3178 json

fs/nfsd/nfs3xdr.c in the Linux kernel through 5.10.8, when there is an NFS export of a subdirectory of a filesystem, allows remote attacker…

published 2021-01-19 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-26521

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.4%
EPSS 2.4% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

fs/nfsd/nfs3xdr.c in the Linux kernel through 5.10.8, when there is an NFS export of a subdirectory of a filesystem, allows remote attackers to traverse to other parts of the filesystem via READDIRPLUS. NOTE: some parties argue that such a subdirectory export is not intended to prevent this attack; see also the exports(5) no_subtree_check default behavior

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 5.10.12-1

debian advisories DEBIAN-CVE-2021-3178

  • linux Ubuntu 16.04 LTS 4.4.0-204.236
  • linux Ubuntu 18.04 LTS 4.15.0-137.141
  • linux Ubuntu 20.04 LTS 5.4.0-67.75
  • linux-aws Ubuntu 16.04 LTS 4.4.0-1123.137
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1095.102
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1039.41
  • linux-gcp Ubuntu 16.04 LTS 4.15.0-1094.107~16.04.1
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1038.41

ubuntu advisories UBUNTU-CVE-2021-3178

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • linux Arch Linux 5.10.10.arch1-1
  • linux-hardened Arch Linux 5.10.10.hardened1-1
  • linux-zen Arch Linux 5.10.10.zen1-1
  • linux-lts Arch Linux 5.4.92-1

arch linux advisories AVG-1466AVG-1467AVG-1468AVG-1469

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3178 updated cvss 5.7

kernel: path traversal in fs/nfsd/nfs3xdr.c may lead to Information Disclosure or RCE

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, kernel-alt, python-perf, +9 more
    affected: workaround, no fix planned “When export subdirectory of a filesystem, enable subtree_check option of the NFS server for preventing possibility of accessing outside of this export.”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: workaround, no fix available “When export subdirectory of a filesystem, enable subtree_check option of the NFS server for preventing possibility of accessing outside of this export.”
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.45% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
NVD 2.0 5.5 AV:N/AC:L/Au:S/C:P/I:P/A:N

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.