Published server without connection limits
At a glance
Base severity
Area
Platform
Evidence level
Benchmark reference
Reads the export, not the device
ConfigProof reads a configuration export. This control is evaluated against the objects in that file, and it reports what the file says. It does not connect to the device and sees no traffic, so a finding here describes the configuration, not what the firewall is doing right now.
Why it matters
Without embryonic connection limits a SYN flood against a published server fills the connection table of the firewall and the server.
How to fix it
Web interface
The steps below are written for the web interface. A finding raised on your own export carries the same steps with your object names filled in.
- In ASDM: Configuration > Firewall > Service Policy Rules > Add, match the published servers' traffic, and in Rule Actions > Connection Settings set the maximum embryonic connections. Apply and save.
- On the CLI: class-map PUBLISHED, match access-list <list>, then in policy-map global_policy class PUBLISHED, set connection embryonic-conn-max <n> per-client-embryonic-max <n>, and write memory.
Command line
Cisco ASA CLI
configure terminalclass-map <class-map>match access-list <access-list>exitpolicy-map global_policyclass <class-map>set connection embryonic-conn-max <embryonic-limit>endwrite memory
An example. Values in angle brackets are yours to supply; a finding on your own export fills in the names it read. Typed in configuration mode; write memory saves it, with no separate commit. Read every line first.
Read it back
show service-policy globalValues to fill in3
- <class-map>
- The class map for the traffic
- <access-list>
- The access list
- <embryonic-limit>
- The maximum embryonic connections
Before you type it2
- Written from the ASA 9.x command reference and not run on a device: read each line before you paste it.
- In multiple context mode, type it in the context it applies to (changeto context <name>).
How to confirm the fix
- Run show service-policy and confirm the class counts connections.
Limits
- No limitation is recorded for this control beyond the one that applies to all of them: it reads a configuration export.
Compliance references
CIS Cisco ASA 9.x Firewall Benchmark v1.1.0
Covers part of the recommendation
Where a control aligns with a recommendation of the CIS Cisco ASA 9.x Firewall Benchmark v1.1.0, that recommendation is cited as a reference. Only that version was checked. A reference is not a certification.
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