CVE-2026-42859

HIGHNVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit probability: 0.5%, top 56% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
8.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.1Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security type 129 (RSA-AES-256) handshake with an oversized client RSA public key, causing rsa_aes_send_challenge in src/auth/rsa-aes.c to overflow a 1024-byte on-stack buffer when encrypting the server challenge. This results in at least a denial of service via server crash. This vulnerability is fixed in 0.9.6.

CVSS v3
8.1
EG Score
8.1(medium)
EG Risk
52(Track)
EG Risk 52/100SSVC: 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 computed
Severity81% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
44%
KEV
Not listed

Published

May 11, 2026

Last Modified

May 13, 2026

Advisory Details (2)

Auto-updated May 11, 2026
Patch available. Sources: github.
github Patch Available

Buffer overflow due to oversized RSA public keys · Advisory · any1/neatvnc · GitHub

https://github.com/any1/neatvnc/security/advisories/GHSA-567c-gpv8-qh9h
generic

auth: rsa-aes: Fix potential buffer overflow · any1/neatvnc@1f6cd6b · GitHub

https://github.com/any1/neatvnc/commit/1f6cd6b75cc167fed3a19a9d1552a1f662f6b337

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
neatvnc0.5.4+dfsg-1 ... 1.0.1+dfsg-1 (17 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
neatvnc0.9.1+dfsg-1, 0.9.1+dfsg-1.1, 1.0.0+dfsg-1~exp1, 1.0.1+dfsg-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
neatvnc0.9.1+dfsg-10.9.1+dfsg-1.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 27× 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.

Showing the most recent 100 of 146 total refreshes for this CVE.

  1. 2026-09-13 16:47 UTCEPSS rescore
  2. 2026-09-12 15:01 UTCEPSS rescore
  3. 2026-09-11 14:53 UTCEPSS rescore
  4. 2026-09-11 12:23 UTCOSV refresh
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  1. 2026-08-17 11:10 UTCEG score recompute
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  22. 2026-08-05 19:17 UTCEPSS rescore
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  25. 2026-08-03 19:26 UTCEG score recompute
  26. 2026-08-03 10:36 UTCEPSS rescore
  27. 2026-08-02 13:02 UTCEG score recompute
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  40. 2026-07-23 03:12 UTCEG score recompute
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  48. 2026-07-16 03:23 UTCOSV refresh
  49. 2026-07-15 16:57 UTCEPSS rescore
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  73. 2026-06-23 21:33 UTCEPSS rescore
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  75. 2026-06-22 14:25 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-42859?
CVE-2026-42859 is a high vulnerability published on May 11, 2026. Neat VNC is a VNC server library. Prior to 0.9.6, a pre-authentication stack buffer overflow exists in neatvnc in the RSA-AES security type handler. An unauthenticated remote attacker who can reach the VNC listening socket can send a crafted security type 5 (RSA-AES) or security type 129…
When was CVE-2026-42859 disclosed?
CVE-2026-42859 was first published in the National Vulnerability Database on May 11, 2026, with the most recent update on May 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42859 actively exploited?
CVE-2026-42859 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 55.6% of all scored CVEs.
What is the CVSS score of CVE-2026-42859?
CVE-2026-42859 has a CVSS v3 base score of 8.1 (NVD).
How do I remediate CVE-2026-42859?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42859, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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