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.

CVSS v4.0

8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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

CVSS v3.1

8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

0.98% chance of exploitation in the next 30 days, 60th percentile

Published

2026-06-29

Updated

2026-07-14

Proof-of-concept exploits (1)

• https://jivasecurity.com/writeups/frontaccounting-rce-attachment-upload-cve-2026-40521

References

• CVE Record
• NVD entry

Related

• CVE-2026-40517
• CVE-2026-40522
• CVE-2026-40501
• CVE-2026-40523
• CVE-2026-40491
• CVE-2026-40524