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Fencer Vulns
critical 9.8

CVE-2018-21029 json

systemd 239 through 245 accepts any certificate signed by a trusted certificate authority for DNS Over TLS.

published 2019-10-30 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-13551

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

systemd 239 through 245 accepts any certificate signed by a trusted certificate authority for DNS Over TLS. Server Name Indication (SNI) is not sent, and there is no hostname validation with the GnuTLS backend. NOTE: This has been disputed by the developer as not a vulnerability since hostname validation does not have anything to do with this issue (i.e. there is no hostname to be sent)

Patch / fix

  • systemd_project systemd 244
  • systemd Debian 14, Debian 13, Debian 12 244-1

debian advisories DEBIAN-CVE-2018-21029

  • systemd openSUSE Tumbleweed 249.4-2.2

opensuse advisories openSUSE-SU-2024:11420-1

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-2018-21029 updated cvss 6.3

systemd: incorrect certificate validation results in acceptance of any certificate signed by a trusted certificate authority for DNS over TLS

  • Red Hat Enterprise Linux 7 systemd, libgudev1, systemd-libs, systemd-sysv, systemd-python, systemd-networkd, +2 more Red Hat Enterprise Linux 8 systemd, systemd-pam, systemd-libs, systemd-udev, systemd-tests, systemd-container, +1 more Red Hat OpenShift Container Platform 4 systemd, systemd-pam, systemd-libs, systemd-oomd, systemd-udev, systemd-tests, +7 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

3.14% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/systemd/systemd/blob/v243/man/resolved.conf.xml#L196-L207 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/systemd/systemd/blob/v239/man/resolved.conf.xml#L199-L207 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness
  • CWE-295 Improper Certificate Validation

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.