The TFTP implementation on Cisco Small Business SPA30x, SPA50x, SPA51x phones 7.5.7 improperly validates firmware-image file integrity, which allows local users to load a Trojan horse image by leveraging shell access, aka Bug ID CSCut67400.
Conclusion & alert: CVE-2015-6403 is rated Low Risk (39.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.38%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-06-15 | 0.09% | 0.38% | +0.29% |
| 2 | 2025-07-02 | 0.37% | 0.09% | -0.28% |
| 3 | 2025-03-30 | — | 0.37% | — |
Full EPSS history (7 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.2 | 2.0 | HIGH |
|
3.9 | 10.0 | [email protected] |
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| cisco | spa500_firmware | 7.5.7 | cpe:2.3:o:cisco:spa500_firmware:7.5.7:*:*:*:*:*:*:* |
| cisco | spa300_firmware | 7.5.7 | cpe:2.3:o:cisco:spa300_firmware:7.5.7:*:*:*:*:*:*:* |