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TI-2026-32070 Aliases CVE-2026-44042GHSA-gh7j-9w79-xm55

UltraVNC repeater wi_uudecode off-by-one in base64 decode boundary check

Priority LOW 18CWE-193Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
None · None · Low
Fix status
No fix listed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

UltraVNC repeater through 1.8.2.2 contains an off-by-one error in the Base64 decode helper used for HTTP Basic authentication. In repeater/webgui/webutils.c:817, the wi_uudecode() function checks whether the input length exceeds the output buffer with a strict greater-than comparison (>), while the correct check should be greater-than-or-equal (>=). When strlen(authdata) equals sizeof(decode), the decoded output length (approximately 3/4 of input) does not overflow the buffer in current practice because the outer HTTP request bounds constrain the Authorization header. However, the defective check leaves a latent off-by-one condition that could become exploitable if the buffering constraints change. The current risk is limited to a one-byte write at the boundary of a 1024-byte stack buffer under constrained conditions.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00491 42nd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
uvncUltraVNCup to 1.8.2.2—No fix listedCNA
  • UltraVNC Vendoruvnc Affected up to 1.8.2.2 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*up to 1.8.2.2Vulnerableuvnc
  • cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:* Versions up to 1.8.2.2 Vulnerable ·uvnc

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-44042
  2. 2026-10-03 Alias added: GHSA-gh7j-9w79-xm55

References

Advisory 1

Other 2

  • TI-2020-19268 UltraVNC Launcher 1.2.4.0 - 'RepeaterHost' Denial of Service CVSS 4.0MEDIUM 6.7
  • TI-2026-04323 UltraVNC Service version.dll uncontrolled search path CVSS 4.0HIGH 7.3
  • TI-2020-19267 UltraVNC Launcher 1.2.4.0 - 'Password' Denial of Service CVSS 4.0MEDIUM 6.7
  • TI-2026-06899 UltraVNC repeater HTTP server global buffer overflow via long URI (pre-auth RCE) CVSS 4.0CRITICAL 9.3
  • TI-2019-05946 Heap-based buffer overflow in Kaspersky Lab UltraVNC CVSS 3.1CRITICAL 9.8
  • TI-2019-05945 Heap-based buffer overflow in Kaspersky Lab UltraVNC CVSS 3.1CRITICAL 9.8
See all 36 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences