CVE-2018-21029
Publication date 30 October 2019
Last updated 4 August 2025
Ubuntu priority
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)
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| systemd | ||
| 18.04 LTS bionic |
Not affected
|
|
| 16.04 LTS xenial |
Not affected
|
|
| 14.04 LTS trusty |
Not affected
|
Notes
mdeslaur
DNS over TLS not enabled by default in Ubuntu. this is only an issue in v243 because strict mode got introduced (DNSOverTLS=yes). Versions earlier than 243 only implemented opportunistic mode which, according to specs, might or not validate the resolver and can also be downgraded.
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
9.8 · Critical
|
| Attack vector | Network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity impact | High |
| Availability impact | High |
| Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |