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)
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | systemd | 244-1 | — |
| Debian 13 | systemd | 244-1 | — |
| Debian 12 | systemd | 244-1 | — |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | systemd | 249.4-2.2 | openSUSE-SU-2024:11420-1 |
Advisories 1
- openSUSE-SU-2024:11420-1 libsystemd0-249.4-2.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
References
- https://github.com/systemd/systemd/issues/9397
- https://blog.cloudflare.com/dns-encryption-explained/
- https://github.com/systemd/systemd/blob/v243/src/resolve/resolved-dnstls-gnutls.c#L62-L63
- FEDORA-2019-4c3ce3aa5c vendor-advisory
- https://security.netapp.com/advisory/ntap-20191122-0002/
- https://github.com/systemd/systemd/pull/13870
- https://github.com/systemd/systemd/blob/v243/man/resolved.conf.xml#L196-L207
- https://github.com/systemd/systemd/blob/v239/man/resolved.conf.xml#L199-L207
- https://tools.ietf.org/html/rfc7858#section-4.1