Answer in brief
CVE-2026-128321 records a Unknown severity vulnerability in Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow vulnerability. The current sources do not mark it as known exploited. The current feed maps Glavsoft (TightVNC)/TightVNC (generic), UltraVNC/UltraVNC (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Glavsoft (TightVNC)/TightVNC (generic), UltraVNC/UltraVNC (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Glavsoft (TightVNC)/TightVNCgeneric | >=1.3.10 <=1.3.10 | Not reported |
| UltraVNC/UltraVNCgeneric | >=1.8.2.4 <=1.8.2.6 | Not reported |
Published upstream
Nov 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Nov 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Nov 13, 2026
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.
Quoted source text, attributed separately from HOL analysis.