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Fencer Vulns
medium 4.4

CVE-2026-18508 json

Tar: tar: --one-top-level hardlink targets not confined to top-level directory enabling arbitrary file overwrite

published 2026-08-03 3 mo ago modified 2026-11-05 3 d ago also EUVD-2026-52327

cvss
4.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

A flaw was found in GNU tar. When extracting an archive with the --one-top-level option, hardlink targets are not confined to the designated top-level directory and may resolve relative to the extraction working directory. A crafted archive can create hardlinks that escape the intended boundary and, when combined with a preexisting symbolic link under the working directory, may allow writing outside that boundary during a single extraction.

Patch / fix

  • Red Hat Red Hat Enterprise Linux 10 2:1.35-13.el10_2
  • Red Hat Red Hat Enterprise Linux 8 2:1.30-13.el8_10
  • Red Hat Red Hat Enterprise Linux 9 2:1.34-13.el9_8
  • Red Hat Red Hat Discovery 2 1788205779
  • Red Hat Red Hat Hardened Images 1.35-9.2.hum1
  • Red Hat Red Hat Update Infrastructure 5 1788765051, 1788880445, 1788880456, 1788880464, 1788880581
  • tar RHEL 8 2:1.30-13.el8_10
  • tar RHEL 10.2 2:1.35-13.el10_2
  • tar RHEL 9 2:1.34-13.el9_8
  • tar hummingbird 1 1.35-9.2.hum1

red hat advisories RHSA-2026:70390RHSA-2026:61586RHSA-2026:61581RHSA-2026:50807

  • tar AlmaLinux 8 2:1.30-13.el8_10
  • tar AlmaLinux 9 2:1.34-13.el9_8
  • tar AlmaLinux 10 2:1.35-13.el10_2

almalinux advisories ALSA-2026:70390ALSA-2026:61581ALSA-2026:61586

  • tar Rocky Linux 8 2:1.30-13.el8_10
  • tar Rocky Linux 10 2:1.35-13.el10_2
  • tar Rocky Linux 9 2:1.34-13.el9_8

rocky linux advisories RLSA-2026:70390RLSA-2026:61586RLSA-2026:61581

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-2026-18508 updated cvss 4.4

tar: tar: --one-top-level hardlink targets not confined to top-level directory enabling arbitrary file overwrite

  • Red Hat Enterprise Linux 6 tar Red Hat Enterprise Linux 7 tar
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Discovery 2 discovery/discovery-server-rhel9 1788205779
    fixed: vendor fix RHSA-2026:61783
  • Red Hat Enterprise Linux BaseOS (v. 8) tar 1.30-13.el8_10
    fixed: vendor fix RHSA-2026:70390
  • Red Hat Enterprise Linux BaseOS (v. 9) tar 1.34-13.el9_8
    fixed: vendor fix RHSA-2026:61581
  • Red Hat Enterprise Linux BaseOS (v. 10) tar 1.35-13.el10_2
    fixed: vendor fix RHSA-2026:61586
  • Red Hat Hardened Images tar 1.35-9.2.hum1
    fixed: vendor fix RHSA-2026:50807
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1788880464, rhui5/rhua-rhel9 1788880581, rhui5/haproxy-rhel9 1788880456, rhui5/installer-rhel9 1788765051, rhui5/cds-kubernetes-rhel9 1788880445
    fixed: vendor fix RHSA-2026:66018
show 1 more
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1788206196 Red Hat Hardened Images rust 1.97.1-2.hum1, chunkah 0.6.0-3.hum1, netavark 2.0.0-3.hum1, nodejs26 26.5.1-1.5.hum1, aardvark-dns 2.0.0-2.hum1, yarnpkg 1.22.22-18.1.hum1, +4 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

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.4 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Discovery 2
  • Red Hat Red Hat Hardened Images
  • Red Hat Red Hat Update Infrastructure 5
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat OpenShift Container Platform 4
  • Red Hat Red Hat OpenShift Container Platform 5

Classification

Weakness
  • CWE-59 Improper Link Resolution Before File Access

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.