CVE-2026-7839
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 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string "adminadmi2" as the admin password via strcpy_s(saved_password, 64, "adminadmi2"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.
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 initializes its HTTP administration server with a hardcoded default password 'adminadmi2' when settings2.txt is absent on first run. The wi_decode_auth() function in the Basic-auth handler accepts this credential without any rate-limiting or account lockout protection, allowing any remote attacker with network access to TCP port 80 to authenticate as administrator and modify repeater configuration including allow/deny rules and session visibility.
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
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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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Identify UltraVNC Repeater installationLocate the UltraVNC Repeater executable (repeater.exe or similar) or service on the system. Common paths may include C:\Program Files\UltraVNC\ or C:\Program Files (x86)\UltraVNC\ on Windows systems.Affected if UltraVNC Repeater is installed and running on the system
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Check installed versionRight-click the repeater executable, select Properties, and verify the File Version. Compare it against the affected version range: any version up to and including 1.8.2.2 is vulnerable.Affected if The installed version is 1.8.2.2 or lower
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Verify settings2.txt presenceLocate the configuration directory for UltraVNC Repeater and check whether the file settings2.txt exists. This file is created after the initial configuration. If absent, the default hardcoded password is active.Affected if settings2.txt is missing, meaning the default password 'adminadmi2' is still in use
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Confirm HTTP admin server exposureUse netstat or a port scanner to verify that TCP port 80 (the HTTP administration interface) is listening and accessible from the network. Check firewall rules to determine if port 80 is exposed externally.Affected if The HTTP admin port 80 is open and network-accessible to untrusted parties
The environment is affected if UltraVNC Repeater version 1.8.2.2 or lower is running with settings2.txt absent and its HTTP admin port 80 is network-accessible, as the hardcoded password 'adminadmi2' would be active and exploitable.
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 dataImmediately change the default admin password from 'adminadmi2' to a strong, unique credential and restrict network access to the HTTP admin port via firewall rules or network segmentation. Implement rate-limiting and account lockout policies in the authentication handler to prevent brute-force attacks.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-7839 — 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-2026-7839 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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- Version or environment caveats, and links to real fixes
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