In a report issued Monday, Jake Reynolds, senior security engineer at FishNet, said the vulnerability affects versions 3.1 and higher of Call Manager, which handles call routing and call signaling functions in Cisco VoIP systems. A lack of input validation and output encoding in the Web administration interface for Call Manager could allow hackers to execute cross-site scripting attacks, Reynolds wrote.
Cross site scripting attacks usually involve tricking users with access privileges into clicking on a URL in an email or Web page.
In a statement, Cisco's Product Security Incident Response Team (PSRIT) recommended that users verify link destinations before clicking on URLs.
Although there are no workarounds for the issue, Cisco has fixed the vulnerability and fixes will be incorporated in all supported CallManager trains in versions 4.3(1), 4.2(3), 4.1(3)SR4 and 3.3(5)SR3, according to the statement.
To guard against attacks, FishNet recommends that companies limit network connectivity to Call Manager wherever possible to prevent hackers from discovering public Web interfaces.
"Simple Google queries are all an attacker needs in this case to obtain the target Call Manager address. There are few compelling reasons one could present that would justify public access to Call Manager web interfaces," according to the report.