CVE-2026-40521
CVE-2026-40521 is a high-severity vulnerability with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.
Key facts
- Severity: High (CVSS 3.x base score 8.8)
- CVSS v4: 8.7
- EPSS exploit prediction: 1% (46th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-22
- Published:
- Last modified:
Description
FrontAccounting before 2.4.20 contains a path traversal vulnerability in the attachment upload handler that allows authenticated attackers to execute arbitrary code by uploading files with traversal sequences in the unique_name parameter. Attackers can supply path traversal sequences ../../../shell.php to write files outside the intended attachments directory into the web root, and by uploading PHP files without extension validation, achieve remote code execution as the web server user.
Frequently asked questions
- What is CVE-2026-40521?
- FrontAccounting before 2.4.20 contains a path traversal vulnerability in the attachment upload handler that allows authenticated attackers to execute arbitrary code by uploading files with traversal sequences in the unique_name parameter. Attackers can supply path traversal sequences ../../../shell.php to write files outside the intended attachments directory into the web root, and by uploading PHP files without extension validation, achieve remote code execution as the web server user.
- How severe is CVE-2026-40521?
- CVE-2026-40521 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-40521 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-40521?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2026-40521 published?
- CVE-2026-40521 was published on 2026-06-29 and last updated on 2026-06-30.
References
- https://github.com/FrontAccountingERP/FA/commit/701fea6848da4a02fb83d30f07a9c0473d6b7e33
- https://jivasecurity.com/writeups/frontaccounting-rce-attachment-upload-cve-2026-40521
- https://sourceforge.net/p/frontaccounting/news/2026/04/release-2420/
- https://www.vulncheck.com/advisories/frontaccounting-path-traversal-rce-via-attachment-upload
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