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Fencer Vulns
medium 6.6

CVE-2021-3782 json

An internal reference count is held on the buffer pool, incremented every time a new buffer is created from the pool.

published 2022-09-23 4 y ago modified 2026-07-25 3 mo ago also EUVD-2021-27046 , JLSEC-2026-97

cvss
6.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

An internal reference count is held on the buffer pool, incremented every time a new buffer is created from the pool. The reference count is maintained as an int; on LP64 systems this can cause the reference count to overflow if the client creates a large number of wl_shm buffer objects, or if it can coerce the server to create a large number of external references to the buffer storage. With the reference count overflowing, a use-after-free can be constructed on the wl_shm_pool tracking structure, where values may be incremented or decremented; it may also be possible to construct a limited oracle to leak 4 bytes of server-side memory to the attacking client at a time.

Patch / fix

  • julia Wayland_jll 1.21.0+0
  • wayland wayland 1.20.91
  • wayland Debian 14, Debian 13, Debian 12 1.21.0-1

debian advisories DEBIAN-CVE-2021-3782

  • wayland Ubuntu 18.04 LTS 1.16.0-1ubuntu1.1~18.04.4
  • wayland Ubuntu 20.04 LTS 1.18.0-1ubuntu0.1
  • wayland Ubuntu 22.04 LTS 1.20.0-1ubuntu0.1
  • wayland Ubuntu Pro 16.04 LTS 1.12.0-1~ubuntu16.04.3+esm1

ubuntu advisories UBUNTU-CVE-2021-3782

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • wayland RHEL 8 1.21.0-1.el8
  • libwayland-egl RHEL 8 1.21.0-1.el8
  • libwayland-client RHEL 8 1.21.0-1.el8
  • libwayland-cursor RHEL 8 1.21.0-1.el8
  • libwayland-server RHEL 8 1.21.0-1.el8

red hat advisories RHSA-2023:2786

  • wayland SLES for SAP 15 SP3, SLES for SAP 15 SP2, SLES 15 SP3-LTSS +10 more 1.18.0-150200.3.3.1
  • wayland SLES for SAP 12 SP5, SLES 12 SP5, SLE Software Development Kit 12 SP5 1.13.0-3.3.1
  • wayland SLE Module for Basesystem 15 SP4, SLE Micro 5.4, SLE Micro 5.3 +2 more 1.19.0-150400.3.3.1
  • wayland SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLE High Performance Computing 15 SP1-LTSS 1.16.0-150100.7.3.1

suse advisories SUSE-SU-2023:1874-1SUSE-SU-2023:1873-1SUSE-SU-2023:1864-1SUSE-SU-2023:1860-1

  • libwayland-egl AlmaLinux 8 1.21.0-1.el8
  • libwayland-client AlmaLinux 8 1.21.0-1.el8
  • libwayland-cursor AlmaLinux 8 1.21.0-1.el8
  • libwayland-server AlmaLinux 8 1.21.0-1.el8

almalinux advisories ALSA-2023:2786

  • wayland Rocky Linux 8 1.21.0-1.el8

rocky linux advisories RLSA-2023:2786

  • wayland CBL-Mariner 2.0 1.21.0-1

azure linux advisories AZL-11019

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-3782 updated cvss 6.6

wayland: libwayland-server wl_shm reference-count overflow

  • Red Hat Enterprise Linux 7 wayland, libwayland-egl, libwayland-client, libwayland-cursor, libwayland-server Red Hat Enterprise Linux 9 libwayland-egl, libwayland-client, libwayland-cursor, libwayland-server
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux AppStream (v. 8) wayland 1.21.0-1.el8, libwayland-egl 1.21.0-1.el8, libwayland-client 1.21.0-1.el8, libwayland-cursor 1.21.0-1.el8, libwayland-server 1.21.0-1.el8
    fixed: vendor fix RHSA-2023:2786

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
17 mo ago

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • gitlab.freedesktop.org https://gitlab.freedesktop.org/wayland/wayland/-/issues/224 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.6 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
NVD 3.1 6.6 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
CNA 3.1 6.6 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
OSV 3.1 6.6 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H

Affected packages

ecosystem package affected fixed in
julia Wayland_jll
<1.21.0+0
1.21.0+0

Affected products

  • n/a wayland

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.