EUVD-2026-39908Severity by source
AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Local IPC attack requires same-session process; low privileges suffice; impact is availability-only crash with no confirmed data disclosure.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Lifecycle Timeline
3DescriptionCVE.org
Notepad++ is a free and open-source source code editor. Prior to 8.9.6.1, a local process in the same interactive Windows session can send a malformed WM_COPYDATA message to Notepad++ using the COPYDATA_FULL_CMDLINE path. The handler appears to process COPYDATASTRUCT.lpData as an unbounded NUL-terminated wchar_t* instead of enforcing COPYDATASTRUCT.cbData. This vulnerability is fixed in 8.9.6.1.
AnalysisAI
Notepad++ versions prior to 8.9.6.1 can be crashed by any local process sharing the same interactive Windows session via a malformed WM_COPYDATA message. The COPYDATA_FULL_CMDLINE handler in NppBigSwitch.cpp dereferences COPYDATASTRUCT.lpData as an unbounded NUL-terminated wchar_t* without validating against the COPYDATASTRUCT.cbData length field, enabling an out-of-bounds read that results in process termination. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires a process running within the same interactive Windows desktop session as the target Notepad++ instance (AV:L). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 base score of 5.0 (Medium) reflects a local attack vector (AV:L), low attack complexity (AC:L), low privilege requirement (PR:L), and required user interaction (UI:R), with impact limited to availability (A:H). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a low-privileged process running in the same interactive Windows desktop session as Notepad++ enumerates top-level windows to locate the Notepad++ main window handle, then calls SendMessage with WM_COPYDATA, setting dwData to COPYDATA_FULL_CMDLINE and providing an lpData buffer that is not NUL-terminated within the cbData-specified length. Notepad++'s WM_COPYDATA handler reads the wchar_t* past the buffer boundary, triggering an access violation and crashing the editor, causing loss of any unsaved work. … |
| Remediation | Upgrade Notepad++ to version 8.9.6.1, which is the vendor-released patch confirmed by GitHub Security Advisory GHSA-r39g-3mcw-xcg2 and commit f20a0888a92ce557a339b833cd9d9d8e97dc797d. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-125 – Out-of-bounds Read
View allSame technique Buffer Overflow
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External POC / Exploit Code
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