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CVE-2026-5525 Notepad++ Project CVE debrief

A stack-based buffer overflow vulnerability exists in Notepad++ version 8.9.3 in the file drop handler component. When a user drags and drops a directory path of exactly 259 characters without a trailing backslash, the application appends a backslash and null terminator without proper bounds checking, resulting in a stack buffer overflow and application crash (STATUS_STACK_BUFFER_OVERRUN).

Vendor
Notepad++ Project
Product
Notepad++
CVSS
MEDIUM 6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-10
Original CVE updated
2026-06-05
Advisory published
2026-04-10
Advisory updated
2026-06-05

Who should care

Users of Notepad++ version 8.9.3

Technical summary

The vulnerability is caused by improper bounds checking in the file drop handler component of Notepad++ version 8.9.3. An attacker can exploit this vulnerability by dragging and dropping a directory path of exactly 259 characters without a trailing backslash, causing a stack buffer overflow and application crash.

Defensive priority

Medium

Recommended defensive actions

  • Update to a patched version of Notepad++
  • Avoid dragging and dropping directory paths of exactly 259 characters without a trailing backslash

Evidence notes

CVE-2026-5525 has a CVSS score of 6 and a severity of MEDIUM. The vulnerability was published on 2026-04-10T08:16:26.067Z and modified on 2026-06-05T13:54:59.610Z.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-5525 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-5525

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-5525 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-5525

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://github.com/notepad-plus-plus/notepad-plus-plus/commit/bfe7514d68bc559534c046c4ef2d1865267aa2b0

    33c584b5-0579-4c06-b2a0-8d8329fcab9c - Patch

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://github.com/notepad-plus-plus/notepad-plus-plus/issues/17921

    33c584b5-0579-4c06-b2a0-8d8329fcab9c - Issue Tracking, Exploit, Mitigation, Vendor Advisory

  • Mitigation or vendor reference

    Unverified legacy reference

    URL: https://github.com/notepad-plus-plus/notepad-plus-plus/pull/17930

    33c584b5-0579-4c06-b2a0-8d8329fcab9c - Issue Tracking, Patch

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.