Description
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.
Analysis
No analysis available yet.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| uvnc | UltraVNC | unaffected |
|
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Remediation
No remediation available yet.
Tracking
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Advisories
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References
| Link | Providers |
|---|---|
| https://github.com/ultravnc/UltraVNC |
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| https://uvnc.com/ |
|
History
Wed, 01 Jul 2026 05:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token | |
| Weaknesses | CWE-787 | |
| References |
| |
| Metrics |
cvssV3_1
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Subscriptions
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MITRE
Status: PUBLISHED
Assigner: securin
Published:
Updated: 2026-07-01T03:33:22.888Z
Reserved: 2026-05-05T03:40:57.359Z
Link: CVE-2026-7829
Vulnrichment
No data.
NVD
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Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
-
CWE-787
Out-of-bounds Write