# UltraVNC vulnerabilities

Source: https://junglewise.ai/threats/vendors/ultravnc  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Updated: 13 November 2026, 03:07 UTC. Rebuilt every hour.  
Data: https://junglewise.ai/threats/vendors/ultravnc.json  
License: CC BY 4.0 with a link back

Junglewise Threat Intelligence has tracked 11 vulnerabilities in UltraVNC: 1 in the last 7 days and 1 in the last 90 days, 2 of them critical and 0 exploited in the wild. The most recent, CVE-2026-128321, was published on 13 November 2026. Nothing was published in the last eight weeks. 2 technologies have a page of their own.

## Counts

- Last 7 days: 1
- Last 30 days: 1
- Last 90 days: 1
- All time: 11 (2 critical, 0 exploited in the wild)

## About UltraVNC

UltraVNC is a developer of open-source remote administration and desktop sharing software for Microsoft Windows.

## Latest UltraVNC vulnerabilities

- [CVE-2026-128321: TightVNC and UltraVNC heap-based buffer overflow in Tight JPEG decoding](https://junglewise.ai/threats/cve-2026-128321-tight-jpeg-decoding-in-tightvnc-and-ultravnc-viewers-contains-a) (info, published 13 Nov 2026)
- [CVE-2026-7840: UltraVNC Repeater global buffer overflow in HTTP administration server](https://junglewise.ai/threats/cve-2026-7840-ultravnc-repeater-global-buffer-overflow-in-http-administration) (critical, CVSS 9.8, published 1 Jul 2026)
- [CVE-2026-7839: UltraVNC Repeater hardcoded password in HTTP administration server](https://junglewise.ai/threats/cve-2026-7839-ultravnc-repeater-hardcoded-password-in-http-administration-server) (critical, CVSS 9.1, published 1 Jul 2026)
- [CVE-2026-7838: UltraVNC viewer heap buffer overflow in RFB failure-response parsing](https://junglewise.ai/threats/cve-2026-7838-ultravnc-viewer-heap-buffer-overflow-in-rfb-failure-response) (high, CVSS 8.8, published 1 Jul 2026)
- [CVE-2026-7831: UltraVNC Viewer off-by-one stack buffer overflow in RFB handler](https://junglewise.ai/threats/cve-2026-7831-ultravnc-viewer-off-by-one-stack-buffer-overflow-in-rfb-handler) (high, CVSS 7.6, published 1 Jul 2026)
- [CVE-2026-7830: UltraVNC weak cryptography in MS-Logon II authentication](https://junglewise.ai/threats/cve-2026-7830-ultravnc-weak-cryptography-in-ms-logon-ii-authentication) (high, CVSS 7.4, published 1 Jul 2026)
- [CVE-2026-7829: UltraVNC Repeater out-of-bounds write in allow/deny rule parser](https://junglewise.ai/threats/cve-2026-7829-ultravnc-repeater-out-of-bounds-write-in-allow-deny-rule-parser) (high, CVSS 7.2, published 1 Jul 2026)
- [CVE-2026-7828: UltraVNC Repeater integer overflow in HTTP request logging](https://junglewise.ai/threats/cve-2026-7828-ultravnc-repeater-integer-overflow-in-http-request-logging) (medium, CVSS 5.3, published 1 Jul 2026)
- [CVE-2026-44042: UltraVNC Repeater off-by-one error in HTTP Basic authentication](https://junglewise.ai/threats/cve-2026-44042-ultravnc-repeater-off-by-one-error-in-http-basic-authentication) (low, CVSS 3.7, published 1 Jul 2026)
- [CVE-2026-44041: UltraVNC out-of-bounds read in vncWc2Mb conversion helper](https://junglewise.ai/threats/cve-2026-44041-ultravnc-out-of-bounds-read-in-vncwc2mb-conversion-helper) (medium, CVSS 4.3, published 1 Jul 2026)
- [CVE-2026-44040: UltraVNC weak PRNG in VNC authentication challenge](https://junglewise.ai/threats/cve-2026-44040-ultravnc-weak-prng-in-vnc-authentication-challenge) (medium, CVSS 4.8, published 1 Jul 2026)

## Most severe UltraVNC vulnerabilities

- [CVE-2026-7840: UltraVNC Repeater global buffer overflow in HTTP administration server](https://junglewise.ai/threats/cve-2026-7840-ultravnc-repeater-global-buffer-overflow-in-http-administration) (critical, CVSS 9.8, published 1 Jul 2026)
- [CVE-2026-7839: UltraVNC Repeater hardcoded password in HTTP administration server](https://junglewise.ai/threats/cve-2026-7839-ultravnc-repeater-hardcoded-password-in-http-administration-server) (critical, CVSS 9.1, published 1 Jul 2026)
- [CVE-2026-7838: UltraVNC viewer heap buffer overflow in RFB failure-response parsing](https://junglewise.ai/threats/cve-2026-7838-ultravnc-viewer-heap-buffer-overflow-in-rfb-failure-response) (high, CVSS 8.8, published 1 Jul 2026)
- [CVE-2026-7831: UltraVNC Viewer off-by-one stack buffer overflow in RFB handler](https://junglewise.ai/threats/cve-2026-7831-ultravnc-viewer-off-by-one-stack-buffer-overflow-in-rfb-handler) (high, CVSS 7.6, published 1 Jul 2026)
- [CVE-2026-7830: UltraVNC weak cryptography in MS-Logon II authentication](https://junglewise.ai/threats/cve-2026-7830-ultravnc-weak-cryptography-in-ms-logon-ii-authentication) (high, CVSS 7.4, published 1 Jul 2026)
- [CVE-2026-7829: UltraVNC Repeater out-of-bounds write in allow/deny rule parser](https://junglewise.ai/threats/cve-2026-7829-ultravnc-repeater-out-of-bounds-write-in-allow-deny-rule-parser) (high, CVSS 7.2, published 1 Jul 2026)
- [CVE-2026-7828: UltraVNC Repeater integer overflow in HTTP request logging](https://junglewise.ai/threats/cve-2026-7828-ultravnc-repeater-integer-overflow-in-http-request-logging) (medium, CVSS 5.3, published 1 Jul 2026)
- [CVE-2026-44040: UltraVNC weak PRNG in VNC authentication challenge](https://junglewise.ai/threats/cve-2026-44040-ultravnc-weak-prng-in-vnc-authentication-challenge) (medium, CVSS 4.8, published 1 Jul 2026)
- [CVE-2026-44041: UltraVNC out-of-bounds read in vncWc2Mb conversion helper](https://junglewise.ai/threats/cve-2026-44041-ultravnc-out-of-bounds-read-in-vncwc2mb-conversion-helper) (medium, CVSS 4.3, published 1 Jul 2026)
- [CVE-2026-44042: UltraVNC Repeater off-by-one error in HTTP Basic authentication](https://junglewise.ai/threats/cve-2026-44042-ultravnc-repeater-off-by-one-error-in-http-basic-authentication) (low, CVSS 3.7, published 1 Jul 2026)

## Vulnerabilities per week

Nothing was published in the last eight weeks.

| Week of | Vulns | Critical | Exploited |
| --- | --- | --- | --- |
| 17 Aug 2026 | 0 | 0 | 0 |
| 24 Aug 2026 | 0 | 0 | 0 |
| 31 Aug 2026 | 0 | 0 | 0 |
| 7 Sep 2026 | 0 | 0 | 0 |
| 14 Sep 2026 | 0 | 0 | 0 |
| 21 Sep 2026 | 0 | 0 | 0 |
| 28 Sep 2026 | 0 | 0 | 0 |
| 5 Oct 2026 | 0 | 0 | 0 |
| 12 Oct 2026 | 0 | 0 | 0 |
| 19 Oct 2026 | 0 | 0 | 0 |
| 26 Oct 2026 | 0 | 0 | 0 |
| 2 Nov 2026 | 0 | 0 | 0 |
| 9 Nov 2026 | 1 | 0 | 0 |

## UltraVNC technologies

- [UltraVNC Repeater](https://junglewise.ai/threats/technologies/repeater): 5 vulnerabilities
- [UltraVNC](https://junglewise.ai/threats/technologies/ultravnc): 4 vulnerabilities

## Sources

NVD, GitHub Security Advisories, OSV, the CISA Known Exploited Vulnerabilities catalog, FIRST EPSS and vendor advisories. Rebuilt every hour. Cite as: Junglewise Threat Intelligence, "UltraVNC vulnerabilities", https://junglewise.ai/threats/vendors/ultravnc, 13 November 2026.