CVE-2026-128321 Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow vulnerability
No CVSS score yet. EPSS 0.2% estimated probability of exploitation activity in the next 30 days.
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.
- EPSS
- 0.2% estimated probability of exploitation activity in the next 30 days; 10th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- Published
- Assigned by
- certcc (CNA)
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
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Affected
- glavsoft (tightvnc):tightvnc
- ultravnc:ultravnc
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| UltraVNC | from 1.8.2.4 through 1.8.2.6 |
| Glavsoft (TightVNC) TightVNC | from 1.3.10 through 1.3.10 |
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Ubuntu | 16.04:LTS, 18.04:LTS, 20.04:LTS and 5 more | tightvnc | no fix listed | UBUNTU-CVE-2026-128321 |
From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.