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.
CVE-2026-44042
Score 3.7 from GitHub Security Advisory (severity: LOW) published 2026-07-01. NVD baseline CVSS 3.7; sources differ by 0.0.
- Lower severity and no public exploit yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 3.7
- EG Score
- 3.7(high)
- EG Risk
- 17(Track)EG Risk 17/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity37% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS
- 31.4%
- KEV
- Not listed
Published
July 1, 2026
Last Modified
July 9, 2026
References (3)
- 33c584b5-0579-4c06-b2a0-8d8329fcab9chttps://github.com/ultravnc/UltraVNC
- 33c584b5-0579-4c06-b2a0-8d8329fcab9chttps://uvnc.com/
- 33c584b5-0579-4c06-b2a0-8d8329fcab9chttps://www.securin.io/zero-days/cve-2026-44042-wi-uudecode-off-by-one-bounded-ultravnc-repeater
Vendor Advisories for CVE-2026-44042(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 8× in last 7d / 28× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-23 03:14 UTCEG score recompute
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:24 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-18 10:04 UTCEPSS rescore
- 2026-07-16 20:30 UTCGHSA enrichment
- 2026-07-16 17:03 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 02:00 UTCEPSS rescore
- 2026-07-13 22:30 UTCEPSS rescore
- 2026-07-13 17:28 UTCGHSA enrichment
- 2026-07-13 06:13 UTCEPSS rescore
- 2026-07-12 05:46 UTCEPSS rescore
- 2026-07-11 08:27 UTCEPSS rescore
- 2026-07-10 14:27 UTCGHSA enrichment
- 2026-07-09 19:10 UTCEPSS rescore
- 2026-07-08 15:16 UTCEPSS rescore
- 2026-07-07 13:46 UTCEPSS rescore
- 2026-07-07 11:23 UTCGHSA enrichment
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-05 02:30 UTCEPSS rescore
- 2026-07-04 08:22 UTCGHSA enrichment
- 2026-07-04 06:31 UTCEPSS rescore
Show 3 moreShow fewer
- 2026-07-01 15:07 UTCEPSS rescore
- 2026-07-01 05:22 UTCEG score recompute
- 2026-07-01 05:20 UTCNVD updatefirst tracked
Related CVEs(same CWE)
Same CWE
10 shownCWE-193
Frequently asked(5)
What is CVE-2026-44042?
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Is CVE-2026-44042 actively exploited?
What is the CVSS score of CVE-2026-44042?
How do I remediate CVE-2026-44042?
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-44042
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