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    CVE-2021-1236

    Multiple Cisco products are affected by a vulnerability in the Snort application detection engine that could allow an unauthenticated, remote attacker to bypass the configured policies on an affected system. The vulnerability is due to a flaw in the detection algorithm. An attacker could exploit this vulnerability by sending crafted packets that would flow through an affected system. A successful exploit could allow the attacker to bypass the configured policies and deliver a malicious payload to the protected network.

    Published:Jan 13, 2021
    Last Modified:Aug 11, 2026
    EPS:Jan 13, 2021
    EPSS Score:0.02146
    CVSS Score:5.3

    Affected Products

    Vendor
    Cisco
    Product
    1100-4p Integrated Services Router
    Vendor
    Cisco
    Product
    1100-8p Integrated Services Router
    Vendor
    Cisco
    Product
    1101-4p Integrated Services Router
    Vendor
    Cisco
    Product
    1109-2p Integrated Services Router
    Vendor
    Cisco
    Product
    1109-4p Integrated Services Router
    Vendor
    Cisco
    Product
    1111x-8p Integrated Services Router
    Vendor
    Cisco
    Product
    4221 Integrated Services Router
    Vendor
    Cisco
    Product
    4321 Integrated Services Router
    Vendor
    Cisco
    Product
    4331 Integrated Services Router
    Vendor
    Cisco
    Product
    4351 Integrated Services Router
    Vendor
    Cisco
    Product
    4431 Integrated Services Router
    Vendor
    Cisco
    Product
    4451-x Integrated Services Router
    Vendor
    Cisco
    Product
    4461 Integrated Services Router
    Vendor
    Cisco
    Product
    Csr 1000v
    Vendor
    Cisco
    Product
    Ios Xe
    Vendor
    Cisco
    Product
    Isa 3000
    Vendor
    Cisco
    Product
    Secure Firewall Management Center
    Vendor
    Cisco
    Product
    Secure Firewall Threat Defense
    Vendor
    Snort
    Product
    Snort

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

    Related CVEs

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High