Description
It was found that xorg-x11-server before 1.19.0 including uses memcmp() to check the received MIT cookie against a series of valid cookies. If the cookie is correct, it is allowed to attach to the Xorg session. Since most memcmp() implementations return after an invalid byte is seen, this causes a time difference between a valid and invalid byte, which could allow an efficient brute force attack.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Xorg | xorg-x11-server | 1.19.0 | — |
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 | xorg-server | 2:1.19.2-1 | — |
| Debian 13 | xorg-server | 2:1.19.2-1 | — |
| Debian 12 | xorg-server | 2:1.19.2-1 | — |
| Debian 7 | xorg-server | 2:1.12.4-6+deb7u8 | DLA-1186-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | xorg-server | 2:1.18.4-0ubuntu0.3 | USN-3362-1 |
| Ubuntu 16.04 LTS | xorg-server-hwe-16.04 | 2:1.18.4-1ubuntu6.1~16.04.2 | USN-3362-1 |
| Ubuntu 14.04 LTS | xorg-server | 2:1.15.1-0ubuntu2.9 | USN-3362-1 |
| Ubuntu 14.04 LTS | xorg-server-lts-xenial | 2:1.18.3-1ubuntu2.3~trusty2 | USN-3362-1 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP2 | xorg-x11-server | 7.6_1.18.3-71.1 | SUSE-SU-2017:1675-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 12 SP2 | xorg-x11-server | 7.6_1.18.3-71.1 | SUSE-SU-2017:1675-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | xorg-x11-server | 1.20.13-1.2 | openSUSE-SU-2024:11525-1 |
Advisories 4
- USN-3362-1 xorg-server, xorg-server-hwe-16.04, xorg-server-lts-xenial vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- DLA-1186-1 xorg-server - security update Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2024:11525-1 xorg-x11-server-1.20.13-1.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2017:1675-1 Security update for xorg-x11-server SUSE / openSUSE Security Updates · Feb 4, 2026
References
- GLSA-201704-03 vendor-advisory
- https://gitlab.freedesktop.org/xorg/xserver/commit/d7ac755f0b618eb1259d93c8a16ec6e39a18627c
- 1037919 vdb-entry
- [debian-lts-announce] 20171122 [SECURITY] [DLA 1186-1] xorg-server security update mailing-list
- GLSA-201710-30 vendor-advisory
- 96480 vdb-entry
- https://www.x41-dsec.de/lab/advisories/x41-2017-001-xorg/
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-2624