CVE-2017-6766

A vulnerability in the Secure Sockets Layer (SSL) Decryption and Inspection feature of Cisco Firepower System Software 5.4.0, 5.4.1, 6.0.0, 6.1.0, 6.2.0, 6.2.1, and 6.2.2 could allow an unauthenticated, remote attacker to bypass the SSL policy for decrypting and inspecting traffic on an affected system. The vulnerability is due to unexpected interaction with Known Key and Decrypt and Resign configuration settings of SSL policies when the affected software receives unexpected SSL packet headers. An attacker could exploit this vulnerability by sending a crafted SSL packet through an affected device in a valid SSL session. A successful exploit could allow the attacker to bypass the SSL decryption and inspection policy for the affected system, which could allow traffic to flow through the system without being inspected. Cisco Bug IDs: CSCve12652.

Published: 2017-08-07 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2017-6766 is rated Moderate Risk (53.1/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.16%). EPSS rose +1.01% 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-2017-6766

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 0.15% 1.16% +1.01%
2 2025-03-19 0.14% 0.15% +0.02%
3 2023-03-07 — 0.14% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2017-6766

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.0 HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:N 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:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2017-6766

Affected software / configurations for CVE-2017-6766

Vendor Product Version Raw CPE
cisco firesight_system_software 5.4.0 cpe:2.3:a:cisco:firesight_system_software:5.4.0:*:*:*:*:*:*:*
cisco firesight_system_software 5.4.1 cpe:2.3:a:cisco:firesight_system_software:5.4.1:*:*:*:*:*:*:*
cisco firesight_system_software 6.0.0 cpe:2.3:a:cisco:firesight_system_software:6.0.0:*:*:*:*:*:*:*
cisco firesight_system_software 6.1.0 cpe:2.3:a:cisco:firesight_system_software:6.1.0:*:*:*:*:*:*:*
cisco firesight_system_software 6.2.0 cpe:2.3:a:cisco:firesight_system_software:6.2.0:*:*:*:*:*:*:*
cisco firesight_system_software 6.2.1 cpe:2.3:a:cisco:firesight_system_software:6.2.1:*:*:*:*:*:*:*
cisco firesight_system_software 6.2.2 cpe:2.3:a:cisco:firesight_system_software:6.2.2:*:*:*:*:*:*:*

References for CVE-2017-6766

cvelogic Threat Intelligence