CVE-2020-3585: Cisco Firepower 1000 Series Bleichenbacher Attack Vulnerability

Severity: low (CVSS 3.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-10-21 · updated 2026-08-11
Weakness: CWE-203

Description

A vulnerability in the TLS handler of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software for Cisco Firepower 1000 Series firewalls could allow an unauthenticated, remote attacker to gain access to sensitive information. The vulnerability is due to improper implementation of countermeasures against the Bleichenbacher attack for cipher suites that rely on RSA for key exchange. An attacker could exploit this vulnerability by sending crafted TLS messages to the device, which would act as an oracle and allow the attacker to carry out a chosen-ciphertext attack. A successful exploit could allow the attacker to perform cryptanalytic operations that may allow decryption of previously captured TLS sessions to the affected device. To exploit this vulnerability, an attacker must be able to perform both of the following actions: Capture TLS traffic that is in transit between clients and the affected device Actively establish a considerable number of TLS connections to the affected device

Affected products

Cisco ASA Software: before 9.13.1.13; from 9.14 before 9.14.1.30 — fixed in 9.13.1.13, 9.14.1.30
Cisco Firepower Threat Defense: from 6.5.0 before 6.5.0.5; from 6.6.0 before 6.6.1 — fixed in 6.5.0.5, 6.6.1
Cisco Firepower Threat Defense Software: before 6.4.0.10 — fixed in 6.4.0.10

How to fix

Upgrade to a fixed version: Cisco ASA Software 9.13.1.13, 9.14.1.30; Cisco Firepower Threat Defense 6.5.0.5, 6.6.1; Cisco Firepower Threat Defense Software 6.4.0.10. Check the vendor advisory for mitigations.

References

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