LibVNCServer UltraZip Encoding Heap Out-of-bounds Read
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- Low · None · Low
- Fix status
- Partial Red Hat: 3 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.
Summary
LibVNCServer versions 0.9.15 and prior (fixed in commit 009008e) contain a heap out-of-bounds read vulnerability in the UltraZip encoding handler that allows a malicious VNC server to cause information disclosure or application crash. Attackers can exploit improper bounds checking in the HandleUltraZipBPP() function by manipulating subrectangle header counts to read beyond the allocated heap buffer.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| LibVNC | LibVNCServer | up to 0.9.15 | — | Patch available | CNA |
- LibVNCServer VendorLibVNC Affected up to 0.9.15 Fixed in — Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:libvncserver_project:libvncserver:*:*:*:*:*:*:*:* | before 0.9.15 | Vulnerable | Libvncserver Project |
- cpe:2.3:a:libvncserver_project:libvncserver:*:*:*:*:*:*:*:* Versions before 0.9.15 Vulnerable ·Libvncserver Project
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix planned: Will not fix |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
Not affected: 1 product
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-02 Threatist record created from CVE-2026-32853
References
More LibVNC vulnerabilities
- TI-2026-37265 libvncclient Tight decoder has an attacker-controlled heap out-of-bounds write CVSS 3.1HIGH 8.8
- TI-2019-11774 Heap-based buffer overflow in LibVNCServer CVSS 3.1HIGH 8.8
- TI-2026-32847 LibVNCClient Tight Gradient decoding allows malicious server-triggered heap/stack OOB writes CVSS 3.1HIGH 8.8
Sources
- CVE-2026-32853 · CVE Program
- CVE-2026-32853 · NVD
- FIRST EPSS
- CVE-2026-32853 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences