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CVE-2023-3138

22
FAUCET Score

CVE-2023-3138 is an out-of-bounds write vulnerability in libX11, affecting Red Hat Enterprise Linux and X.Org libX11. The flaw stems from insufficient bounds checking in src/InitExt.c, where functions trust Xserver-provided IDs as array indexes, potentially leading to memory corruption within the Display structure. With a CVSS score of 7.5 (High), this vulnerability can be exploited remotely with low complexity, resulting in a denial of service (client crash). There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.8.6CPE matchmatch criteria
cpe:2.3:a:x.org:libx11:*:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.66%
Probability of exploitation in next 30 days
EPSS Percentile
74.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0166 is in the 56th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (5)

microsoftpatch availablevia msrc
Product: cbl2 libX11 1.6.12-6 on CBL Mariner 2.0Fixed in: 1.6.12-6
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: libX11-0:1.6.8-6.el8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.8 Extended Update SupportFixed in: libX11-0:1.6.8-6.el8_8
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: libX11-0:1.7.0-8.el9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 9.2 Extended Update SupportFixed in: libX11-0:1.7.0-8.el9_2
View patch

Vendor Advisories (2)

redhatCVE-2023-3138Moderate

libX11: InitExt.c can overwrite unintended portions of the Display structure if the extension request leads to a buffer overflow

Jun 15, 2023
microsoft2023-Jun/CVE-2023-3138Important

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.

Jun 13, 2023

References

access.redhat.com / security/cve/CVE-2023-3138
Third Party Advisory
gitlab.freedesktop.org / xorg/lib/libx11/-/commit/304a654a0d57bf0f00d8998185f0360332cfa36c
Patch
lists.x.org / archives/xorg-announce/2023-June/003406.html
Mailing ListPatch
lists.x.org / archives/xorg-announce/2023-June/003407.html
Mailing ListPatch
security.netapp.com / advisory/ntap-20231208-0008