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CVE-2026-7830

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, which multiplies three libc rand() values seeded from
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:e0da76ebe0cede175a93482f0050e86038ded1bb592dcd3885f93b24f6d7ceb1
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cwe · 2 assertions

{"cweId":"CWE-326","description":"Inadequate Encryption Strength","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/problemTypes/0/descriptions/0

{"cweId":"CWE-338","description":"Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/problemTypes/1/descriptions/0

Affected products and versions

1 source assertion
{"defaultStatus":"unaffected","modules":["winvnc","ms-logon"],"product":"UltraVNC","vendor":"uvnc","versions":[{"lessThanOrEqual":"1.8.2.2","status":"affected","version":"0","versionType":"custom"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.4,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/metrics/0/cvssV3_1

CWE assertions

2 source assertions
{"cweId":"CWE-326","description":"Inadequate Encryption Strength","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/problemTypes/0/descriptions/0
{"cweId":"CWE-338","description":"Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/problemTypes/1/descriptions/0

Source references

3 source assertions
{"name":"UltraVNC source repository","tags":["product"],"url":"https://github.com/ultravnc/UltraVNC"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/references/1
{"name":"UltraVNC project page","tags":["vendor-advisory"],"url":"https://uvnc.com/"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/references/0
{"url":"https://www.securin.io/zero-days/cve-2026-7830-31-bit-dh-weak-rng-ms-logon-credential-interception-ultravnc"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:a73fc0870379c3102a13c9100f683322abb49506b22aa296bae52589276df088 · sha256:17c97f1e407ff3d4… · /containers/cna/references/2

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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