Description
LookupCol.c in X.Org X through X11R7.7 and libX11 before 1.7.1 might allow remote attackers to execute arbitrary code. The libX11 XLookupColor request (intended for server-side color lookup) contains a flaw allowing a client to send color-name requests with a name longer than the maximum size allowed by the protocol (and also longer than the maximum packet size for normal-sized packets). The user-controlled data exceeding the maximum size is then interpreted by the server as additional X protocol requests and executed, e.g., to disable X server authorization completely. For example, if the victim encounters malicious terminal control sequences for color codes, then the attacker may be able to take full control of the running graphical session.
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 | libx11 | 2:1.7.1-1 | — |
| Debian 13 | libx11 | 2:1.7.1-1 | — |
| Debian 12 | libx11 | 2:1.7.1-1 | — |
| Debian 10 | libx11 | 2:1.6.7-1+deb10u2 | DSA-4920-1 |
| Debian 9 | libx11 | 2:1.6.4-3+deb9u4 | DLA-2666-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | libx11 | 2:1.6.9-2ubuntu1.2 | USN-4966-1 |
| Ubuntu 18.04 LTS | libx11 | 2:1.6.4-3ubuntu0.4 | USN-4966-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | libx11 | 2:1.6.3-1ubuntu2.2+esm1 | USN-4966-2 |
| Ubuntu Pro 14.04 LTS | libx11 | 2:1.6.2-1ubuntu2.1+esm2 | USN-4966-2 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | libX11 +3 | 1.6.8-5.el8 | RHSA-2021:4326 |
| RHEL 7 | libX11 +2 | 1.6.7-4.el7_9 | RHSA-2021:3296 |
| RHEL 7 | redhat-virtualization-host +1 | 4.3.18-20210903.0.el7_9 | RHSA-2021:3477 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 8 | libX11 +3 | 1.6.8-5.el8 | ALSA-2021:4326 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | libX11 | 1.6.8-5.el8 | RLSA-2021:4326 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | libX11 | 1.6.5-3.18.1 | SUSE-SU-2021:1897-1, SUSE-SU-2021:1765-1 |
| SLES 15 SP2 | libX11 | 1.6.5-3.18.1 | SUSE-SU-2021:1897-1, SUSE-SU-2021:1765-1 |
| SLES 15 SP1 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SLES 15 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SLES 12 SP5 | libX11 | 1.6.2-12.18.1 | SUSE-SU-2021:1892-1, SUSE-SU-2021:1766-1 |
Show 22 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP4 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SLES 12 SP3 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SLES 12 SP2 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SLES 11 SP4 | xorg-x11-libX11 | 7.4-5.11.72.27.1 | SUSE-SU-2021:14748-1 |
| SLES for SAP 15 SP1 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SLES for SAP 15 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SLES for SAP 12 SP5 | libX11 | 1.6.2-12.18.1 | SUSE-SU-2021:1892-1, SUSE-SU-2021:1766-1 |
| SLES for SAP 12 SP4 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SLES for SAP 12 SP3 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SLE Micro 5.0 | libX11 | 1.6.5-3.18.1 | SUSE-SU-2021:1897-1, SUSE-SU-2021:1765-1 |
| SLE HPC 15 SP1 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SLE HPC 15 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SUSE OpenStack Cloud Crowbar 9 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SUSE OpenStack Cloud Crowbar 8 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SUSE OpenStack Cloud 9 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SUSE OpenStack Cloud 8 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SUSE Manager Server 4.0 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SUSE Manager Retail Branch Server 4.0 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SUSE Manager Proxy 4.0 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | xorg-x11-libX11 | 7.4-5.11.72.27.1 | SUSE-SU-2021:14748-1 |
| SUSE HPE Helion OpenStack 8 | libX11 | 1.6.2-12.21.1 | SUSE-SU-2021:1892-1 |
| SUSE Enterprise Storage 6 | libX11 | 1.6.5-3.21.1 | SUSE-SU-2021:1897-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | libX11 | 1.7.2-1.2 | openSUSE-SU-2024:10918-1 |
| openSUSE Leap 15.3 | libX11 | 1.6.5-3.21.1 | openSUSE-SU-2021:1897-1 |
| openSUSE Leap 15.2 | libX11 | 1.6.5-lp152.5.15.1 | openSUSE-SU-2021:0857-1, openSUSE-SU-2021:0807-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | libx11 | 1.7.1-r0 | — |
| Alpine v3.23 | libx11 | 1.7.1-r0 | — |
| Alpine v3.22 | libx11 | 1.7.1-r0 | — |
| Alpine v3.21 | libx11 | 1.7.1-r0 | — |
| Alpine v3.20 | libx11 | 1.7.1-r0 | — |
Show 10 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | libx11 | 1.7.1-r0 | — |
| Alpine v3.18 | libx11 | 1.7.1-r0 | — |
| Alpine v3.17 | libx11 | 1.7.1-r0 | — |
| Alpine v3.16 | libx11 | 1.7.1-r0 | — |
| Alpine v3.15 | libx11 | 1.7.1-r0 | — |
| Alpine v3.14 | libx11 | 1.7.1-r0 | — |
| Alpine v3.13 | libx11 | 1.7.1-r0 | — |
| Alpine v3.12 | libx11 | 1.6.12-r1 | — |
| Alpine v3.11 | libx11 | 1.6.12-r1 | — |
| Alpine v3.10 | libx11 | 1.6.12-r1 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | libX11 +2 | 1.6.7-3.amzn2.0.2 | ALAS2-2021-1686 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | libX11 +3 | 1.6.8-5.el8 | ELSA-2021-4326 |
| Oracle Linux 7 | libX11 +2 | 1.6.7-4.el7_9 | ELSA-2021-3296 |
Advisories 23
- ALSA-2021:4326 Moderate: libX11 security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2021:3477 Red Hat Security Advisory: RHV-H security update (redhat-virtualization-host) 4.3.18 Red Hat Security Advisories (RHSA) · Aug 26, 2026
- USN-4966-2 libx11 vulnerability Ubuntu Security Notices (USN) · Jun 29, 2026
- RHSA-2021:4326 Red Hat Security Advisory: libX11 security update Red Hat Security Advisories (RHSA) · Jun 29, 2026
- RHSA-2021:3296 Red Hat Security Advisory: libX11 security update Red Hat Security Advisories (RHSA) · Jun 29, 2026
- USN-4966-1 libx11 vulnerability Ubuntu Security Notices (USN) · Apr 22, 2026
- DSA-4920-1 libx11 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-2666-1 libx11 - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:4326 Moderate: libX11 security update Rocky Linux Security Advisories · Feb 4, 2026
- openSUSE-SU-2021:1897-1 Security update for libX11 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10918-1 libX11-6-1.7.2-1.2 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0857-1 Security update for libX11 SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0807-1 Security update for libX11 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:1892-1 Security update for libX11 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:14748-1 Security update for xorg-x11-libX11 SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:1897-1 Security update for libX11 SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2023-0063 Juniper Junos Space: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 8, 2025
- SUSE-SU-2021:1765-1 Security update for libX11 SUSE / openSUSE Security Updates · May 2, 2025
- SUSE-SU-2021:1766-1 Security update for libX11 SUSE / openSUSE Security Updates · May 2, 2025
- WID-SEC-2024-1591 Juniper JUNOS: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 11, 2024
- ELSA-2021-4326 Moderate: libX11 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 16, 2021
- ELSA-2021-3296 Important: libX11 security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Aug 30, 2021
- ALAS2-2021-1686 Important: libX11 security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jul 15, 2021
References
- https://unparalleled.eu/publications/2021/advisory-unpar-2021-1.txt
- https://lists.freedesktop.org/archives/xorg/
- [oss-security] 20210518 libX11 security advisory: May 18, 2021 mailing-list
- 20210520 CVE-2021-31535 libX11 Insufficient Length Checks PoC and Archeology mailing-list
- http://packetstormsecurity.com/files/162737/libX11-Insufficient-Length-Check-Injection.html
- [debian-lts-announce] 20210524 [SECURITY] [DLA 2666-1] libx11 security update mailing-list
- DSA-4920 vendor-advisory
- GLSA-202105-16 vendor-advisory
- https://www.openwall.com/lists/oss-security/2021/05/18/3
- https://www.openwall.com/lists/oss-security/2021/05/18/2
- https://unparalleled.eu/blog/2021/20210518-using-xterm-to-navigate-the-huge-color-space/
- https://lists.x.org/archives/xorg-announce/2021-May/003088.html
- https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/8d2e02ae650f00c4a53deb625211a0527126c605
- https://security.netapp.com/advisory/ntap-20210813-0001/
- FEDORA-2021-62bb9998b2 vendor-advisory
- [kafka-dev] 20210831 Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker image mailing-list
- [kafka-users] 20210831 Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker image mailing-list
- [kafka-users] 20210901 Re: [EXTERNAL] Re: Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker image mailing-list
- [kafka-dev] 20210901 Re: [EXTERNAL] Re: Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker image mailing-list