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.