CVE-2023-6683 | Qemu: vnc: null pointer dereference in qemu_clipboard_request()

A flaw was found in the QEMU built-in VNC server while processing ClientCutText messages. The qemu_clipboard_request() function can be reached before vnc_server_cut_text_caps() was called and had the chance to initialize the clipboard peer, leading to a NULL pointer dereference. This could allow a malicious authenticated VNC client to crash QEMU and trigger a denial of service.

Published: 2024-01-12 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-6683 is rated Moderate Risk (50.2/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.26%). EPSS rose +1.19% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-6683

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.07% 1.26% +1.19%
2 2025-11-21 0.55% 0.07% -0.47%
3 2025-11-18 — 0.55% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-6683

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]

Weakness enumeration for CVE-2023-6683

OS Trackers for CVE-2023-6683

vendor priority summary link
alpine — CVE-2023-6683: 1 source package rows (qemu); 56 state rows across 3 repos (3.19-community, 3.22-community, edge-community); fixed 0, open 56. https://security.alpinelinux.org/vuln/CVE-2023-6683
debian unimportant CVE-2023-6683 unimportant priority: Debian including 1 source packages (qemu), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-6683
redhat medium — https://access.redhat.com/security/cve/CVE-2023-6683
suse medium — https://www.suse.com/security/cve/CVE-2023-6683/
ubuntu medium CVE-2023-6683 medium priority: Ubuntu including 1 source packages (qemu), 9 status rows across 9 suites (bionic, focal, jammy, lunar, mantic, noble, trusty, upstream, xenial): not-affected 5, ignored 2, released 2. https://ubuntu.com/security/CVE-2023-6683

Affected software / configurations for CVE-2023-6683

Vendor Product Version Raw CPE
qemu qemu >= 6.1.0, < 8.2.2 cpe:2.3:a:qemu:qemu:*:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
redhat enterprise_linux 9.0 cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*

References for CVE-2023-6683

cvelogic Threat Intelligence