CVE-2026-128321
Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow vulnerability
Description
Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting in application crash and potentially other memory-corruption impacts.
INFO
Published Date :
Nov. 13, 2026, 2:18 a.m.
Last Modified :
Nov. 13, 2026, 2:18 a.m.
Remotely Exploit :
No
Source :
[email protected]
Solution
- Update TightVNC viewer to the latest version.
- Update UltraVNC viewer to the latest version.
- Avoid connecting to untrusted VNC servers.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-128321.
| URL | Resource |
|---|---|
| https://github.com/ultravnc/ultravnc | |
| https://www.tightvnc.com/ | |
| https://www.kb.cert.org/vuls/id/644655 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-128321 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-128321
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-128321 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-128321 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Nov. 13, 2026
Action Type Old Value New Value Added Description Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting in application crash and potentially other memory-corruption impacts. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/128xxx/CVE-2026-128321.json">CVE-2026-128321</a> Added Reference https://github.com/ultravnc/ultravnc Added Reference https://www.tightvnc.com/ -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 13, 2026
Action Type Old Value New Value Added Reference https://www.kb.cert.org/vuls/id/644655