Patch tracker / CVE reference / CVE-2026-34346

CVE-2026-34346

CVE-2026-34346 is a medium severity Microsoft vulnerability with a CVSS score of 5.5. Its EPSS score puts the probability of exploitation in the next 30 days at 64%. Microsoft has shipped the fix: deploy one of the 10 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.

Risk summary

Medium

5.5

CVSS

64%

EPSS, 30 days

Medium

Severity

Not in the CISA KEV catalog. EPSS exploit probability 64%. CVSS 5.5 (Medium).

This CVE is among the top half of tracked Microsoft CVEs by EPSS exploit probability.

Senserva AI Opinion for CVE-2026-34346

CVE-2026-34346 is an information disclosure flaw in the Ancillary Function Driver for WinSock (afd.sys), the kernel driver that backs Windows socket operations, affecting Windows 10 Version 1809 and Windows Server 2019. The CVSS 5.5 Medium score and the driver involved point to local information leakage rather than remote exploitation, meaning an attacker would need existing code execution on the box first. It is not on the CISA KEV list and has no known ransomware association, so this is patch-on-schedule rather than drop-everything.

Do this: Deploy the current cumulative update for Windows 10 1809 and Server 2019 to systems still on that build, prioritizing multi-user or shared machines where a local attacker could benefit from leaked kernel memory.

AI-generated from public data, 2026-07-21. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2026-34346

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I am an IT admin assessing a vulnerability. Facts for CVE-2026-34346 (source: https://senserva.com/cve/CVE-2026-34346.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2026-34346: Medium severity Microsoft vulnerability, CVSS 5.5
- EPSS 30-day exploitation probability: 64%
- Actively exploited (CISA KEV): no
- Fixed by: KB5099414, KB5099444, KB5099445, KB5099535, KB5099536, KB5099538, KB5099539, KB5099540, KB5101649, KB5101650
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) What to patch or mitigate first. 4) How to check whether my devices are exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch this cycle

Not confirmed exploited yet, but the 30-day exploit probability is high (EPSS 64%).

Fixed by KB5099414 and 9 more (by build, listed below). Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.

Do this now: Patch in this maintenance window; do not let it slip to the next one.

Official patch(es) for CVE-2026-34346

High priority: EPSS puts the odds of near-term exploitation high. In Intune or Defender, confirm whether the fixing updates KB5099414, KB5099444, KB5099445, KB5099535, KB5099536, KB5099538, KB5099539, KB5099540, KB5101649, KB5101650 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.

Apply the Microsoft security updates below to fix CVE-2026-34346. Each KB page carries the Microsoft Update Catalog download, Microsoft's known issues for the update, a copy-paste PowerShell check for whether it is installed, and the Senserva AI read.

KB5099414 KB5099444 KB5099445 KB5099535 KB5099536 KB5099538 KB5099539 KB5099540 KB5101649 KB5101650

Scope and sources

Affected products

Fixed by the same updates

CVE-2026-56155 CVE-2026-32202 CVE-2026-50302 CVE-2026-50416 CVE-2026-50419 CVE-2026-57092 CVE-2026-42990 CVE-2026-49172

Authoritative references

Official CVE record (cve.org)NVD detail Microsoft MSRC FIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.