CVE-2021-31535

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.

• CWE-120

• http://packetstormsecurity.com/files/162737/libX11-Insufficient-Length-Check-Injection.htmlExploit, Third Party Advisory, VDB Entry
• http://seclists.org/fulldisclosure/2021/May/52Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/05/18/2Mailing List, Third Party Advisory
• https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/8d2e02ae650f00c4a53deb625211a0527126c605Third Party Advisory
• https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org%3E
• https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.org%3E
• https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org%3E
• https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.org%3E
• https://lists.debian.org/debian-lts-announce/2021/05/msg00021.htmlThird Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TEOT4RLB76RVPJQKGGTIKTBIOLHX2NR6/
• https://lists.freedesktop.org/archives/xorg/Third Party Advisory
• https://lists.x.org/archives/xorg-announce/2021-May/003088.htmlVendor Advisory
• https://security.gentoo.org/glsa/202105-16Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210813-0001/Third Party Advisory
• https://unparalleled.eu/blog/2021/20210518-using-xterm-to-navigate-the-huge-color-space/Exploit, Third Party Advisory
• https://unparalleled.eu/publications/2021/advisory-unpar-2021-1.txtExploit, Third Party Advisory
• https://www.debian.org/security/2021/dsa-4920Third Party Advisory
• https://www.openwall.com/lists/oss-security/2021/05/18/2Mailing List, Third Party Advisory
• https://www.openwall.com/lists/oss-security/2021/05/18/3Mailing List, Third Party Advisory
• http://packetstormsecurity.com/files/162737/libX11-Insufficient-Length-Check-Injection.htmlExploit, Third Party Advisory, VDB Entry
• http://seclists.org/fulldisclosure/2021/May/52Mailing List, Third Party Advisory
• http://www.openwall.com/lists/oss-security/2021/05/18/2Mailing List, Third Party Advisory
• https://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/8d2e02ae650f00c4a53deb625211a0527126c605Third Party Advisory
• https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org%3E
• https://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.org%3E
• https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org%3E
• https://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.org%3E
• https://lists.debian.org/debian-lts-announce/2021/05/msg00021.htmlThird Party Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TEOT4RLB76RVPJQKGGTIKTBIOLHX2NR6/
• https://lists.freedesktop.org/archives/xorg/Third Party Advisory
• https://lists.x.org/archives/xorg-announce/2021-May/003088.htmlVendor Advisory
• https://security.gentoo.org/glsa/202105-16Third Party Advisory
• https://security.netapp.com/advisory/ntap-20210813-0001/Third Party Advisory
• https://unparalleled.eu/blog/2021/20210518-using-xterm-to-navigate-the-huge-color-space/Exploit, Third Party Advisory
• https://unparalleled.eu/publications/2021/advisory-unpar-2021-1.txtExploit, Third Party Advisory
• https://www.debian.org/security/2021/dsa-4920Third Party Advisory
• https://www.openwall.com/lists/oss-security/2021/05/18/2Mailing List, Third Party Advisory
• https://www.openwall.com/lists/oss-security/2021/05/18/3Mailing List, Third Party Advisory

Published

May 27, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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