UltraVNC repeater through 1.8.2.2 contains an integer overflow in the HTTP request logging path. In repeater/webgui/settings.c:336, the win_log() function allocates list nodes via malloc(sizeof(struct LIST) + strlen(line)), where line is derived from HTTP request URIs. If strlen(line) is sufficiently large, the addition overflows to a value smaller than sizeof(struct LIST), causing a heap allocation smaller than required. The subsequent strcpy of the full string into the undersized allocation produces a heap buffer overflow. In the current implementation this overflow is bounded by the HTTP receive buffer size (WI_RXBUFSIZE = 153600 bytes, well below SIZE_MAX on 32-bit builds), limiting practical exploitability to a partial heap write. A remote unauthenticated attacker can trigger the theoretical overflow path by sending a maximally-sized URI in an HTTP request to the repeater HTTP port.
Metrics
Affected Vendors & Products
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References
| Link | Providers |
|---|---|
| https://github.com/ultravnc/UltraVNC |
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| https://uvnc.com/ |
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History
Wed, 01 Jul 2026 05:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | UltraVNC repeater through 1.8.2.2 contains an integer overflow in the HTTP request logging path. In repeater/webgui/settings.c:336, the win_log() function allocates list nodes via malloc(sizeof(struct LIST) + strlen(line)), where line is derived from HTTP request URIs. If strlen(line) is sufficiently large, the addition overflows to a value smaller than sizeof(struct LIST), causing a heap allocation smaller than required. The subsequent strcpy of the full string into the undersized allocation produces a heap buffer overflow. In the current implementation this overflow is bounded by the HTTP receive buffer size (WI_RXBUFSIZE = 153600 bytes, well below SIZE_MAX on 32-bit builds), limiting practical exploitability to a partial heap write. A remote unauthenticated attacker can trigger the theoretical overflow path by sending a maximally-sized URI in an HTTP request to the repeater HTTP port. | |
| Title | UltraVNC repeater integer overflow in win_log malloc leading to heap overflow | |
| Weaknesses | CWE-190 | |
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| Metrics |
cvssV3_1
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MITRE
Status: PUBLISHED
Assigner: securin
Published:
Updated: 2026-07-01T03:33:21.648Z
Reserved: 2026-05-05T03:40:50.298Z
Link: CVE-2026-7828
Vulnrichment
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NVD
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Redhat
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OpenCVE Enrichment
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