CVE-2026-7829UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser.
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.2 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-787
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Jul 9, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
uvnc ultravnc uvnc:ultravnc | through 1.8.2.2 | NVD |
References
- https://github.com/ultravnc/UltraVNCproduct
- https://uvnc.com/product, release-notes
- https://www.securin.io/zero-days/cve-2026-7829-post-auth-oob-nul-write-repeater-rule-parser-ultravnc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.