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Vulnerability record · CVE-2018-21029 · published 30 October 2019

CVE-2018-21029: Systemd project systemd improper certificate validation vulnerability

Systemd Project · Systemd

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)

9.8 CVSS 3.1 Critical EPSS 3.1% · top 12.6% CWE-295 · Improper certificate validation
9.8CVSS 3.1 base score, v2 7.5
3.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
18References, 4 tagged exploit
17 Jun 2026Last modified by NVD

Description

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)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://blog.cloudflare.com/dns-encryption-explained/ Third Party Advisory
https://github.com/systemd/systemd/blob/v239/man/resolved.conf.xml#L199-L207 ExploitThird Party Advisory
https://github.com/systemd/systemd/blob/v243/man/resolved.conf.xml#L196-L207 ExploitThird Party Advisory
https://github.com/systemd/systemd/blob/v243/src/resolve/resolved-dnstls-gnutls.c#L62-L63 PatchThird Party Advisory
https://github.com/systemd/systemd/issues/9397 Issue TrackingThird Party Advisory
https://github.com/systemd/systemd/pull/13870 PatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4NLJVOJMB6ANDILRLDZK26Y
https://security.netapp.com/advisory/ntap-20191122-0002/ Third Party Advisory
https://tools.ietf.org/html/rfc7858#section-4.1 Third Party Advisory
https://blog.cloudflare.com/dns-encryption-explained/ Third Party Advisory
https://github.com/systemd/systemd/blob/v239/man/resolved.conf.xml#L199-L207 ExploitThird Party Advisory
https://github.com/systemd/systemd/blob/v243/man/resolved.conf.xml#L196-L207 ExploitThird Party Advisory
https://github.com/systemd/systemd/blob/v243/src/resolve/resolved-dnstls-gnutls.c#L62-L63 PatchThird Party Advisory
https://github.com/systemd/systemd/issues/9397 Issue TrackingThird Party Advisory
https://github.com/systemd/systemd/pull/13870 PatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4NLJVOJMB6ANDILRLDZK26Y
https://security.netapp.com/advisory/ntap-20191122-0002/ Third Party Advisory
https://tools.ietf.org/html/rfc7858#section-4.1 Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2018-21029), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.