Critical severity9.8NVD Advisory· Published May 27, 2021· Updated Jun 17, 2026
CVE-2021-31535
CVE-2021-31535
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
42- X.Org/libX11description
- Range: <= X11R7.7
- osv-coords39 versionspkg:rpm/almalinux/libX11pkg:rpm/almalinux/libX11-commonpkg:rpm/almalinux/libX11-develpkg:rpm/almalinux/libX11-xcbpkg:rpm/opensuse/libX11&distro=openSUSE%20Leap%2015.2pkg:rpm/opensuse/libX11&distro=openSUSE%20Leap%2015.3pkg:rpm/opensuse/libX11&distro=openSUSE%20Tumbleweedpkg:rpm/suse/libX11&distro=HPE%20Helion%20OpenStack%208pkg:rpm/suse/libX11&distro=SUSE%20Enterprise%20Storage%206pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP1-ESPOSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015%20SP1-LTSSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015-ESPOSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20High%20Performance%20Computing%2015-LTSSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Micro%205.0pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Basesystem%2015%20SP2pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Module%20for%20Basesystem%2015%20SP3pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2012%20SP2-BCLpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2012%20SP3-BCLpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2012%20SP3-LTSSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2012%20SP4-LTSSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2012%20SP5pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP1-BCLpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2015%20SP1-LTSSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%2015-LTSSpkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2012%20SP3pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2012%20SP4pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2012%20SP5pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Server%20for%20SAP%20Applications%2015%20SP1pkg:rpm/suse/libX11&distro=SUSE%20Linux%20Enterprise%20Software%20Development%20Kit%2012%20SP5pkg:rpm/suse/libX11&distro=SUSE%20Manager%20Proxy%204.0pkg:rpm/suse/libX11&distro=SUSE%20Manager%20Retail%20Branch%20Server%204.0pkg:rpm/suse/libX11&distro=SUSE%20Manager%20Server%204.0pkg:rpm/suse/libX11&distro=SUSE%20OpenStack%20Cloud%208pkg:rpm/suse/libX11&distro=SUSE%20OpenStack%20Cloud%209pkg:rpm/suse/libX11&distro=SUSE%20OpenStack%20Cloud%20Crowbar%208pkg:rpm/suse/libX11&distro=SUSE%20OpenStack%20Cloud%20Crowbar%209pkg:rpm/suse/xorg-x11-libX11&distro=SUSE%20Linux%20Enterprise%20Point%20of%20Sale%2011%20SP3pkg:rpm/suse/xorg-x11-libX11&distro=SUSE%20Linux%20Enterprise%20Server%2011%20SP4-LTSS
< 1.6.8-5.el8+ 38 more
- (no CPE)range: < 1.6.8-5.el8
- (no CPE)range: < 1.6.8-5.el8
- (no CPE)range: < 1.6.8-5.el8
- (no CPE)range: < 1.6.8-5.el8
- (no CPE)range: < 1.6.5-lp152.5.15.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.7.2-1.2
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.18.1
- (no CPE)range: < 1.6.5-3.18.1
- (no CPE)range: < 1.6.5-3.18.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.18.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.18.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.2-12.18.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.5-3.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 1.6.2-12.21.1
- (no CPE)range: < 7.4-5.11.72.27.1
- (no CPE)range: < 7.4-5.11.72.27.1
Patches
Vulnerability mechanics
References
19- packetstormsecurity.com/files/162737/libX11-Insufficient-Length-Check-Injection.htmlnvdExploitThird Party AdvisoryVDB Entry
- unparalleled.eu/blog/2021/20210518-using-xterm-to-navigate-the-huge-color-space/nvdExploitThird Party Advisory
- unparalleled.eu/publications/2021/advisory-unpar-2021-1.txtnvdExploitThird Party Advisory
- seclists.org/fulldisclosure/2021/May/52nvdMailing ListThird Party Advisory
- www.openwall.com/lists/oss-security/2021/05/18/2nvdMailing ListThird Party Advisory
- gitlab.freedesktop.org/xorg/lib/libx11/-/commit/8d2e02ae650f00c4a53deb625211a0527126c605nvdThird Party Advisory
- lists.debian.org/debian-lts-announce/2021/05/msg00021.htmlnvdThird Party Advisory
- lists.freedesktop.org/archives/xorg/nvdThird Party Advisory
- lists.x.org/archives/xorg-announce/2021-May/003088.htmlnvdVendor Advisory
- security.gentoo.org/glsa/202105-16nvdThird Party Advisory
- security.netapp.com/advisory/ntap-20210813-0001/nvdThird Party Advisory
- www.debian.org/security/2021/dsa-4920nvdThird Party Advisory
- www.openwall.com/lists/oss-security/2021/05/18/2nvdMailing ListThird Party Advisory
- www.openwall.com/lists/oss-security/2021/05/18/3nvdMailing ListThird Party Advisory
- lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org%3Envd
- lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.org%3Envd
- lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org%3Envd
- lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.org%3Envd
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TEOT4RLB76RVPJQKGGTIKTBIOLHX2NR6/nvd
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