Read the docs
TI-2026-06888 Aliases CVE-2026-7829GHSA-fxj2-5q9g-wmp9

UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token

Priority LOW 35CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
High
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-787 and the CVSS impact.

Summary

UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00852 58th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
uvncUltraVNCup to 1.8.2.2—No fix listedCNA
  • UltraVNC Vendoruvnc Affected up to 1.8.2.2 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*up to 1.8.2.2Vulnerableuvnc
  • cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:* Versions up to 1.8.2.2 Vulnerable ·uvnc

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-7829
  2. 2026-10-03 Alias added: GHSA-fxj2-5q9g-wmp9

References

Advisory 1

Other 2

  • TI-2020-19268 UltraVNC Launcher 1.2.4.0 - 'RepeaterHost' Denial of Service CVSS 4.0MEDIUM 6.7
  • TI-2026-04323 UltraVNC Service version.dll uncontrolled search path CVSS 4.0HIGH 7.3
  • TI-2020-19267 UltraVNC Launcher 1.2.4.0 - 'Password' Denial of Service CVSS 4.0MEDIUM 6.7
  • TI-2026-06899 UltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE) CVSS 4.0CRITICAL 9.3
  • TI-2019-05946 Heap-based buffer overflow in Kaspersky Lab UltraVNC CVSS 3.1CRITICAL 9.8
  • TI-2019-05945 Heap-based buffer overflow in Kaspersky Lab UltraVNC CVSS 3.1CRITICAL 9.8
See all 36 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences