Notepad++: session.xml backupFilePath starts_with Bypass
Notepad++ is a free and open-source source code editor. Prior to 8.9.7, Notepad++ validates the backupFilePath attribute from session.xml with std::wstring::starts_with against the expected backup directory without path normalization, allowing parent-directory sequences during snapshot-mode restoration to read an arbitrary user-readable file outside the backup directory into an editor tab. This issue is fixed in version 8.9.7.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for help- Published
- Aug 17, 2026
- Updated
- Sep 9, 2026
- EPSS
- 0.2% · 5th percentile
- CWE
- CWE-22
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Report tools
Action score
20
Monitor
Low priority for now.
- CVSS
- 20 / 40 · 5.1 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- proof of concept
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · GitHub_M
- 5.1
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.
notepad-plus-plus notepad-plus-plus
- < 8.9.7affected
Same product
notepad-plus-plus: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-85279Notepad++: Stack Buffer Overflow in Plugin Lexer Loading via Unchecked GetLexerCount() Return Value34Monitor
- CVE-2026-57233Notepad++: Path Traversal (Zip Slip) in WinGup Plugin Extraction32Monitor
- CVE-2026-86054Notepad++: Stack Buffer Overflow in `NppParameters::writeSession` via overlong session path31Monitor
- CVE-2026-77605Notepad++ “Run by system” executes *.txt.cmd when user selected *.txt (target confusion → command execution)31Monitor
- CVE-2026-54758Notepad++: Stack Buffer Overflow in expandNppEnvironmentStrs31Monitor
- CVE-2026-85995Notepad++: Authenticode verification bypass allows modified updater execution29Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| notepad-plus-plus notepad-plus-plus | 8.9.7 · description | Vendor (CNA) |
Exploit status
Proof of concept available
A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.
Evidence
- Proof-of-concept repository on GitHub ×1
Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.
| Source | Kind | Date |
|---|---|---|
| Proof-of-concept repository on GitHub | stars:0 | 2026-08-06 |
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
- First PoC-12 d
- Published
- TodaySep 30, 2026+44 d
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-572330 days apartNotepad++: Path Traversal (Zip Slip) in WinGup Plugin Extraction32Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- P
- Scope
- X
Weakness class (CWE)
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')CVSS vector
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
nvd-secondary
Root cause
A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.
The bug in code
The whole CWE-22 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
const file = path.join(ROOT, req.query.name);res.sendFile(file);Fixed
const file = path.resolve(ROOT, req.query.name);if (!file.startsWith(ROOT + path.sep)) { return res.sendStatus(400);}res.sendFile(file);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Path TraversalCAPEC-126likelihood: High · Very High
- Using Slashes and URL Encoding Combined to Bypass Validation LogicCAPEC-64likelihood: High · High
- Manipulating Web Input to File System CallsCAPEC-76likelihood: High · Very High
- Using Escaped Slashes in Alternate EncodingCAPEC-78likelihood: High · High
- Using Slashes in Alternate EncodingCAPEC-79likelihood: High · High
ATT&CK techniques
—
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/notepad-plus-plus/notepad-plus-plus/commit/7e66f36db666a13b09fb5c31232ab2ca1c2ebccc
- github.com/notepad-plus-plus/notepad-plus-plus/releases/tag/v8.9.7
- github.com/notepad-plus-plus/notepad-plus-plus/security/advisories/GHSA-rqfm-pw34-r7j6
Vendor advisories and official records. Exploit/PoC links are deliberately left out.