CVE Explorer
CVE-2026-44040
UltraVNC through 1.8.2.2 uses a cryptographically weak pseudo-random number generator to produce VNC authentication challenge bytes. In rfb/vncauth.c:119-129, the vncRandomBytes() function seeds libc rand() with time(0) + getpid() + rand() and generates a 16-byte challenge. The combined seed space is approximately 31 bits (libc rand() internal state) and is entirely determined by publicly-observable values (wall-clock time and process ID). An attacker who can observe the authentication exchange
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
0
Affected products and versions
1 source assertion{"defaultStatus":"unaffected","modules":["winvnc","vncviewer"],"product":"UltraVNC","vendor":"uvnc","versions":[{"lessThanOrEqual":"1.8.2.2","status":"affected","version":"0","versionType":"custom"}]}
- cve_program_cvelist_v5affectedurn:baitaphish:normalized-source-record:v2:0e40576fab532f4e6b5b80398bed1ff83c9a0eb64dc16a9952df2c8cc117a2ce · sha256:e590311e6f962009… · /containers/cna/affected/0
Provider-owned CVSS observations
1 source assertion{"metric":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.8,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
- cve_program_cvelist_v5cvssurn:baitaphish:normalized-source-record:v2:0e40576fab532f4e6b5b80398bed1ff83c9a0eb64dc16a9952df2c8cc117a2ce · sha256:e590311e6f962009… · /containers/cna/metrics/0/cvssV3_1
CWE assertions
1 source assertion{"cweId":"CWE-338","description":"Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)","lang":"en","type":"CWE"}
- cve_program_cvelist_v5cweurn:baitaphish:normalized-source-record:v2:0e40576fab532f4e6b5b80398bed1ff83c9a0eb64dc16a9952df2c8cc117a2ce · sha256:e590311e6f962009… · /containers/cna/problemTypes/0/descriptions/0
Source references
3 source assertions{"name":"UltraVNC source repository","tags":["product"],"url":"https://github.com/ultravnc/UltraVNC"}
- cve_program_cvelist_v5referenceurn:baitaphish:normalized-source-record:v2:0e40576fab532f4e6b5b80398bed1ff83c9a0eb64dc16a9952df2c8cc117a2ce · sha256:e590311e6f962009… · /containers/cna/references/1
{"name":"UltraVNC project page","tags":["vendor-advisory"],"url":"https://uvnc.com/"}
- cve_program_cvelist_v5referenceurn:baitaphish:normalized-source-record:v2:0e40576fab532f4e6b5b80398bed1ff83c9a0eb64dc16a9952df2c8cc117a2ce · sha256:e590311e6f962009… · /containers/cna/references/0
{"url":"https://www.securin.io/zero-days/cve-2026-44040-libc-rand-weak-rng-vnc-auth-challenge-ultravnc"}
- cve_program_cvelist_v5referenceurn:baitaphish:normalized-source-record:v2:0e40576fab532f4e6b5b80398bed1ff83c9a0eb64dc16a9952df2c8cc117a2ce · sha256:e590311e6f962009… · /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.