Detections
Analytics
CentOS Linux 6 [TuxCare] Security Update: libX11 / libX11-common / libX11-devel Multiple Vulnerabilities (CENTOS6:CLSA-2026:1792609205)
critical Nessus Plugin ID 370883
Synopsis
The CentOS Linux host is missing one or more security updates.Description
The CentOS Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the TuxCare CENTOS6:CLSA-2026:1792609205 advisory.- An issue was discovered in XListExtensions in ListExt.c in libX11 through 1.6.5. A malicious server can send a reply in which the first string overflows, causing a variable to be set to NULL that will be freed later on, leading to DoS (segmentation fault). (CVE-2018-14598)
- An issue was discovered in libX11 through 1.6.5. The function XListExtensions in ListExt.c is vulnerable to an off-by-one error caused by malicious server responses, leading to DoS or possibly unspecified other impact. (CVE-2018-14599)
- An issue was discovered in libX11 through 1.6.5. The function XListExtensions in ListExt.c interprets a variable as signed instead of unsigned, resulting in an out-of-bounds write (of up to 128 bytes), leading to DoS or remote code execution. (CVE-2018-14600)
- 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. (CVE-2021-31535)
- A vulnerability was found in libX11. The security flaw occurs because the functions in src/InitExt.c in libX11 do not check that the values provided for the Request, Event, or Error IDs are within the bounds of the arrays that those functions write to, using those IDs as array indexes. They trust that they were called with values provided by an Xserver adhering to the bounds specified in the X11 protocol, as all X servers provided by X.Org do. As the protocol only specifies a single byte for these values, an out-of- bounds value provided by a malicious server (or a malicious proxy-in-the-middle) can only overwrite other portions of the Display structure and not write outside the bounds of the Display structure itself, possibly causing the client to crash with this memory corruption. (CVE-2023-3138)
Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.
Solution
Update the affected packages based on the guidance in TuxCare advisory CENTOS6:CLSA-2026:1792609205.See Also
Plugin Details
Severity: Critical
ID: 370883
File Name: tuxcare_centos_6_CLSA-2026-1792609205.nasl
Version: 1.1
Type: Local
Agent: unix
Family: CentOS Local Security Checks
Published: 10/22/2026
Updated: 10/22/2026
Supported Sensors: Nessus Agent, Continuous Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 4.9
Percentile: 57.12
Vendor
Vendor Severity: Critical
CVSS v2
Risk Factor: High
Base Score: 7.5
Temporal Score: 5.9
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P
CVSS Score Source: CVE-2021-31535
CVSS v3
Risk Factor: Critical
Base Score: 9.8
Temporal Score: 8.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C
Vulnerability Information
Required KB Items: Host/local_checks_enabled, Host/CentOS/release, Host/CentOS/rpm-list, Host/OS/extended-third-party
Exploit Available: true
Exploit Ease: Exploits are available
Patch Publication Date: 10/21/2026
Vulnerability Publication Date: 8/21/2018
Reference Information
CVE: CVE-2018-14598, CVE-2018-14599, CVE-2018-14600, CVE-2021-31535, CVE-2023-3138, CVE-2023-43787
CLSA: 2026:1792609205