CVE-2018-21029

Exp

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)

Published: 2019-10-30 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-21029 is rated High Exploit Risk (85.9/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 3.14%). 2 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.58% over the last day, indicating growing attacker interest. Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2018-21029

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2018-21029

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 1.56% 3.14% +1.58%
2 2025-11-21 2.49% 1.56% -0.93%
3 2025-11-18 — 2.49% —

Full EPSS history (12 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-21029

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:N)
No account or special rights needed—anonymous or random user is enough.
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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2018-21029

OS Trackers for CVE-2018-21029

vendor priority summary link
debian low CVE-2018-21029 low priority: Debian including 1 source packages (systemd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2018-21029
redhat medium — https://access.redhat.com/security/cve/CVE-2018-21029
ubuntu low CVE-2018-21029 low priority: Ubuntu including 1 source packages (systemd), 6 status rows across 6 suites (bionic, disco, eoan, trusty, upstream, xenial): not-affected 4, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2018-21029

Affected software / configurations for CVE-2018-21029

Vendor Product Version Raw CPE
systemd_project systemd >= 239, < 244 cpe:2.3:a:systemd_project:systemd:*:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*

References for CVE-2018-21029

URL Tags
https://blog.cloudflare.com/dns-encryption-explained/ Third Party Advisory
https://github.com/systemd/systemd/blob/v239/man/resolved.conf.xml#L199-L207 Exploit Third Party Advisory
https://github.com/systemd/systemd/blob/v243/man/resolved.conf.xml#L196-L207 Exploit Third Party Advisory
https://github.com/systemd/systemd/blob/v243/src/resolve/resolved-dnstls-gnutls.c#L62-L63 Patch Third Party Advisory
https://github.com/systemd/systemd/issues/9397 Issue Tracking Third Party Advisory
https://github.com/systemd/systemd/pull/13870 Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4NLJVOJMB6ANDILRLDZK26YGLYBEPHKY/
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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