UBUNTU-CVE-2021-31535

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    UBUNTU-CVE-2021-31535

    Published: 18 May 2021Last Modified: 22 Apr 2026
    Upstream:
    CVE-2021-31535

    Summary:

    Details: 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.

    References: https://ubuntu.com/security/CVE-2021-31535, https://www.openwall.com/lists/oss-security/2021/05/18/2, https://www.openwall.com/lists/oss-security/2021/05/18/3, https://unparalleled.eu/publications/2021/advisory-unpar-2021-1.txt, https://unparalleled.eu/blog/2021/20210518-using-xterm-to-navigate-the-huge-color-space/, https://ubuntu.com/security/notices/USN-4966-1, https://ubuntu.com/security/notices/USN-4966-2, https://www.cve.org/CVERecord?id=CVE-2021-31535

    Affected packages

    Package

    Name: libx11

    Purl: pkg:deb/ubuntu/libx11@2:1.6.2-1ubuntu2.1+esm2?arch=source&distro=trusty/esm

    Affected ranges

    Type: ECOSYSTEM

    Events:

    Introduced- 0
    Fixed -2:1.6.2-1ubuntu2.1+esm2

    Affected versions

    2:1.6.1-1ubuntu1
    2:1.6.1-1ubuntu2
    2:1.6.2-1ubuntu1
    2:1.6.2-1ubuntu2
    2:1.6.2-1ubuntu2.1
    2:1.6.2-1ubuntu2.1+esm1

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    UBUNTU-CVE-2021-31535 | CVE-DB