Researchers at the industrial and IoT cybersecurity company Claroty developed an attack method for getting past the web application firewalls (WAF) of a number of top manufacturers
The method was found while working on the wireless device management platform of Cambium Networks for unrelated research.
A Cambium SQL injection flaw was found by the researchers, who then leveraged it to steal user sessions, SSH keys, password hashes, tokens, and verification codes.
The experts noted that while attempts to hack the cloud version were thwarted by the Amazon Web Services (AWS) WAF, they were successful in exploiting the SQL injection vulnerability against the on-premises version.
The specialists then began looking into ways to get around the AWS WAF.
The researchers found that because the WAF cannot parse JSON syntax, it is possible to get around it by attaching it to SQL injection payloads.
“Using JSON syntax, it is possible to craft new SQLi payloads. These payloads, since they are not commonly known, could be used to fly under the radar and bypass many security tools.” reads the report published by Claroty. “Using syntax from different database engines, we were able to compile the following list of true statements in SQL:
- PostgreSQL: ‘{“b”:2}’::jsonb <@ ‘{“a”:1, “b”:2}’::jsonb Is the left JSON contained in the right one? True.
- SQLite: ‘{“a”:2,”c”:[4,5,{“f”:7}]}’ -> ‘$.c[2].f’ = 7 Does the extracted value of this JSON equals 7? True.
- MySQL: JSON_EXTRACT(‘{“id”: 14, “name”: “Aztalan”}’, ‘$.name’) = ‘Aztalan’ Does the extracted value of this JSON equals to ‘Aztalan’? True.”
Claroty researchers used the JSON operator ‘@<’ to throw the WAF into a loop and supply malicious SQLi payloads.
The researchers verifies that the bypass attack technique also worked against firewalls from other vendors, including Cloudflare, F5, Imperva, and Palo Alto Networks.
“We discovered that the leading vendors’ WAFs did not support JSON syntax in their SQL injection inspection process, allowing us to prepend JSON syntax to a SQL statement that blinded a WAF to the malicious code.” the report concludes.
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