CVE-2015-6321

Cisco AsyncOS before 8.5.7-042, 9.x before 9.1.0-032, 9.1.x before 9.1.1-023, and 9.5.x and 9.6.x before 9.6.0-042 on Email Security Appliance (ESA) devices; before 9.1.0-032, 9.1.1 before 9.1.1-005, and 9.5.x before 9.5.0-025 on Content Security Management Appliance (SMA) devices; and before 7.7.0-725 and 8.x before 8.0.8-113 on Web Security Appliance (WSA) devices allows remote attackers to cause a denial of service (memory consumption) via a flood of TCP packets, aka Bug IDs CSCus79774, CSCus79777, and CSCzv95795.

Published: 2015-11-05 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2015-6321 is rated Moderate Risk (62.9/100): CVSS High severity, with medium exploitation likelihood (EPSS 2.76%). EPSS rose +2.21% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2015-6321

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 0.55% 2.76% +2.21%
2 2026-03-03 1.01% 0.55% -0.45%
3 2025-03-17 — 1.01% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2015-6321

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 2.0 HIGH
AV:N/AC:L/Au:N/C:N/I:N/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 6.9 [email protected]

Weakness enumeration for CVE-2015-6321

Affected software / configurations for CVE-2015-6321

Vendor Product Version Raw CPE
cisco web_security_appliance 5.6.0-623 cpe:2.3:a:cisco:web_security_appliance:5.6.0-623:*:*:*:*:*:*:*
cisco web_security_appliance 6.0.0-000 cpe:2.3:a:cisco:web_security_appliance:6.0.0-000:*:*:*:*:*:*:*
cisco web_security_appliance 7.5.0-000 cpe:2.3:a:cisco:web_security_appliance:7.5.0-000:*:*:*:*:*:*:*
cisco web_security_appliance 7.5.0-825 cpe:2.3:a:cisco:web_security_appliance:7.5.0-825:*:*:*:*:*:*:*
cisco web_security_appliance 7.5.1-000 cpe:2.3:a:cisco:web_security_appliance:7.5.1-000:*:*:*:*:*:*:*
cisco web_security_appliance 7.5.2-000 cpe:2.3:a:cisco:web_security_appliance:7.5.2-000:*:*:*:*:*:*:*
cisco web_security_appliance 7.7.0-000 cpe:2.3:a:cisco:web_security_appliance:7.7.0-000:*:*:*:*:*:*:*
cisco web_security_appliance 7.7.1-000 cpe:2.3:a:cisco:web_security_appliance:7.7.1-000:*:*:*:*:*:*:*
cisco web_security_appliance 8.0.0-000 cpe:2.3:a:cisco:web_security_appliance:8.0.0-000:*:*:*:*:*:*:*
cisco web_security_appliance 8.5.0.000 cpe:2.3:a:cisco:web_security_appliance:8.5.0.000:*:*:*:*:*:*:*
cisco content_security_management_appliance 7.8.0-328 cpe:2.3:a:cisco:content_security_management_appliance:7.8.0-328:*:*:*:*:*:*:*
cisco content_security_management_appliance 7.8.1-001 cpe:2.3:a:cisco:content_security_management_appliance:7.8.1-001:*:*:*:*:*:*:*
cisco content_security_management_appliance 7.9.0-201 cpe:2.3:a:cisco:content_security_management_appliance:7.9.0-201:*:*:*:*:*:*:*
cisco content_security_management_appliance 7.9.2-116 cpe:2.3:a:cisco:content_security_management_appliance:7.9.2-116:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.0.1-031 cpe:2.3:a:cisco:content_security_management_appliance:8.0.1-031:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.1.0-001 cpe:2.3:a:cisco:content_security_management_appliance:8.1.0-001:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.1.1-033 cpe:2.3:a:cisco:content_security_management_appliance:8.1.1-033:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.1.2-000 cpe:2.3:a:cisco:content_security_management_appliance:8.1.2-000:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.2.0-238 cpe:2.3:a:cisco:content_security_management_appliance:8.2.0-238:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.3.0-350 cpe:2.3:a:cisco:content_security_management_appliance:8.3.0-350:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.3.5-061 cpe:2.3:a:cisco:content_security_management_appliance:8.3.5-061:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.3.6-014 cpe:2.3:a:cisco:content_security_management_appliance:8.3.6-014:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.3.7-010 cpe:2.3:a:cisco:content_security_management_appliance:8.3.7-010:*:*:*:*:*:*:*
cisco content_security_management_appliance 8.4.0-150 cpe:2.3:a:cisco:content_security_management_appliance:8.4.0-150:*:*:*:*:*:*:*
cisco content_security_management_appliance 9.0.0-073 cpe:2.3:a:cisco:content_security_management_appliance:9.0.0-073:*:*:*:*:*:*:*
cisco content_security_management_appliance 9.1.0-004 cpe:2.3:a:cisco:content_security_management_appliance:9.1.0-004:*:*:*:*:*:*:*
cisco email_security_appliance 7.6.1-000 cpe:2.3:a:cisco:email_security_appliance:7.6.1-000:*:*:*:*:*:*:*
cisco email_security_appliance 7.6.3-000 cpe:2.3:a:cisco:email_security_appliance:7.6.3-000:*:*:*:*:*:*:*
cisco email_security_appliance 7.7.0-000 cpe:2.3:a:cisco:email_security_appliance:7.7.0-000:*:*:*:*:*:*:*
cisco email_security_appliance 7.7.1-000 cpe:2.3:a:cisco:email_security_appliance:7.7.1-000:*:*:*:*:*:*:*
cisco email_security_appliance 7.8.0-311 cpe:2.3:a:cisco:email_security_appliance:7.8.0-311:*:*:*:*:*:*:*
cisco email_security_appliance 8.5.6-052 cpe:2.3:a:cisco:email_security_appliance:8.5.6-052:*:*:*:*:*:*:*
cisco email_security_appliance 8.6.0-011 cpe:2.3:a:cisco:email_security_appliance:8.6.0-011:*:*:*:*:*:*:*
cisco email_security_appliance 8.9.1-000 cpe:2.3:a:cisco:email_security_appliance:8.9.1-000:*:*:*:*:*:*:*
cisco email_security_appliance 8.9.2-032 cpe:2.3:a:cisco:email_security_appliance:8.9.2-032:*:*:*:*:*:*:*
cisco email_security_appliance 9.0.0-212 cpe:2.3:a:cisco:email_security_appliance:9.0.0-212:*:*:*:*:*:*:*
cisco email_security_appliance 9.0.5-000 cpe:2.3:a:cisco:email_security_appliance:9.0.5-000:*:*:*:*:*:*:*
cisco email_security_appliance 9.1.0-011 cpe:2.3:a:cisco:email_security_appliance:9.1.0-011:*:*:*:*:*:*:*
cisco email_security_appliance 9.4.4-000 cpe:2.3:a:cisco:email_security_appliance:9.4.4-000:*:*:*:*:*:*:*
cisco email_security_appliance 9.5.0-000 cpe:2.3:a:cisco:email_security_appliance:9.5.0-000:*:*:*:*:*:*:*

References for CVE-2015-6321

cvelogic Threat Intelligence