CVE-2026-7828
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedUltraVNC 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceUltraVNC Repeater through 1.8.2.2 has an integer overflow in the HTTP request logging function win_log() in settings.c:336. The malloc calculation sizeof(struct LIST) + strlen(line) overflows when the HTTP URI-derived line is large enough, allocating a heap buffer smaller than required. A subsequent strcpy writes beyond the allocation boundary, causing a heap buffer overflow bounded by the 153600-byte receive buffer. A remote unauthenticated attacker can trigger this by sending a maximally-sized URI to the repeater HTTP port.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data<= 1.8.2.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Locate UltraVNC Repeater installationSearch for the UltraVNC Repeater executable (repeater.exe, uvnc_repeater.exe, or similar) on the system. Check common installation directories such as C:\Program Files\UltraVNC, C:\Program Files (x86)\UltraVNC, or a custom installation path.Affected if The executable is found and matches the affected version range.
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Determine installed versionRight-click the repeater executable, select Properties, and check the Version or Product Version field. Alternatively, run the executable with a version flag if supported (e.g., --version or -v), or check the binary metadata.Affected if The version is 1.8.2.2 or lower.
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Identify if HTTP service is enabledCheck the repeater configuration file (typically repeater.ini or settings.ini in the same directory) for HTTP server settings. Look for parameters such as httpport, HttpPort, or similar that enable the built-in HTTP listener.Affected if HTTP port is configured and enabled (typically port 80, 8080, or similar).
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Verify HTTP port is listeningOpen a command prompt and run 'netstat -an | findstr :80' or 'netstat -an | findstr :8080' (adjust port number based on configuration). Alternatively, use PowerShell Get-NetTCPConnection to check if the repeater HTTP port is in LISTEN state.Affected if The repeater HTTP port is in LISTEN state and accepting connections.
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Assess network exposureReview firewall rules or network access controls to determine if the repeater HTTP port is accessible from untrusted networks. Check if the service is bound to 0.0.0.0 (all interfaces) versus 127.0.0.1 (localhost only).Affected if The HTTP port is accessible from non-local network interfaces without authentication.
You are affected if UltraVNC Repeater version 1.8.2.2 or lower is installed, the HTTP service is enabled, and the HTTP port is exposed to network traffic, allowing a remote attacker to send specially crafted large URI requests.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply any available vendor patch upgrading past version 1.8.2.2. If no patch exists, restrict network access to the repeater HTTP port via firewall or network segmentation to prevent unauthenticated attackers from reaching the service.
- Consultation3.0 h
- Implementation6.0 h
- Testing5.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-7828 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-7828 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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