Authenticated service hang via clipboard decompression loop
Published Sep 13, 2023 · Updated Nov 8, 2025
Denial of service in the QEMU VNC server on Red Hat Enterprise Linux 8 and 9 allows remote authenticated users to hang a virtual machine. vnc_client_cut_text_ext passes attacker-controlled compressed clipboard data to inflate_buffer, whose wrong exit condition keeps looping after zlib returns Z_STREAM_END. Reachability requires an authenticated VNC session capable of sending clipboard data; the resulting CPU loop interrupts the affected QEMU service without reported data access or modification.
Summary
What happened
Denial of service in the QEMU VNC server on Red Hat Enterprise Linux 8 and 9 allows remote authenticated users to hang a virtual machine. vnc_client_cut_text_ext passes attacker-controlled compressed clipboard data to inflate_buffer, whose wrong exit condition keeps looping after zlib returns Z_STREAM_END. Reachability requires an authenticated VNC session capable of sending clipboard data; the resulting CPU loop interrupts the affected QEMU service without reported data access or modification.
The record
- CVE
- CVE-2023-3255
- Published
- Sep 13, 2023
- Updated
- Nov 8, 2025
- Vendor
- Red Hat
- Product
- Red Hat Enterprise Linux 8
- Classifications
- CWE-835, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 13, 2023CVE publishedPublication date reported by the CVE source.
- Nov 8, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo