What is CVE-2026-48770?
A local denial-of-service vulnerability in Notepad++ (versions <= v8.9.6) caused by improper handling of an inter-process WM_COPYDATA message on the COPYDATA_FULL_CMDLINE path. A local process running in the same interactive Windows session can send a malformed WM_COPYDATA message; the handler processes the data as an unbounded NUL-terminated string rather than respecting the declared buffer size (COPYDATASTRUCT.cbData), triggering an out-of-bounds read / crash that reliably causes a local denial of service against notepad++.exe. Fixed in v8.9.6.1. Disclosed by Enrique de Clerck, Leonardo Gutierrez, and Daniel Cifuentes. NOTE: CVE-2026-48770 is a local DoS crash (CWE-125); the arbitrary-code-execution / config.xml commandLineInterpreter issue is a separate CVE (CVE-2026-48778) patched in the same v8.9.6.1 release.
The record classifies CVE-2026-48770 under weakness class CWE-125. Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs a user to take an action first, and has high impact on availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 125 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 5 — MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H - EPSS (FIRST)
- 0.1% probability of exploitation in the next 30 days, higher than 3.0% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-06-26, last modified 2026-06-29
Is CVE-2026-48770 being exploited?
Weaponised exploit code for CVE-2026-48770 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 17 in the Threadlinqs vulnerability feed.
- atiilla/Notepad-8.9.6-PoC (github)
- trickest/cve (trickest)
Affected products and versions
- notepad-plus-plus: notepad-plus-plus
How to fix CVE-2026-48770
No vendor patch reference has been recorded for CVE-2026-48770 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-48770
1 tracked threat in the Threadlinqs corpus references CVE-2026-48770, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, FIRST EPSS, public proof-of-concept repositories. Last verified by Threadlinqs on .