PatchTheCVECVE-2026-7830: UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNC_Ms
CVE-2026-7830 is a high-severity flaw (CVSS 7.4) affecting ultravnc. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNC_MsLogonIIAuth). In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer (DH_MAX_BITS controls the prime size). A 64-bit DH key can be broken by Pollard's rho algorithm in under one second on current hardware. Additionally, the private exponent is generated by the rng() function, whic
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-7830?
ultravnc: upgrade to newer than 1.8.2.2. Exact commands for each OS are on this page.
Is CVE-2026-7830 being exploited?
CVE-2026-7830 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-7830 affect?
CVE-2026-7830 affects ultravnc. Severity is high (CVSS 7.4). UltraVNC through 1.8.2.2 uses inadequate cryptography in the MS-Logon II authentication scheme (rfbUltraVNC_MsLogonIIAuth). In rfb/dh.cpp the Diffie-Hellman key exchange is performed with parameters that fit in an unsigned 64-bit integer (D
How urgent is CVE-2026-7830?
Priority 36/100. High severity; Remotely exploitable, no login, no user action
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