Cisco over the weekend published information on a vulnerability (CVE-2020-3566) in the IOS XR software that could be exploited to cause a denial of service condition.
Cisco has warned that attackers are already attempting to exploit the vulnerability.
The issue resides in the Distance Vector Multicast Routing Protocol (DVMRP) feature of IOS XR. Remote exploitation is possible without authentication, and could result in exhausted process memory and instability of other processes, including those of interior and exterior routing protocols.
According to Cisco, the vulnerability exists due to insufficient queue management for Internet Group Management Protocol (IGMP) packets. As a result, an attacker could send crafted IGMP traffic to a vulnerable device to exploit the flaw.
“This vulnerability affects any Cisco device that is running any release of Cisco IOS XR Software if an active interface is configured under multicast routing,” the company says.
Cisco explains that administrators can use the show igmp interface command to determine whether multicast routing is enabled, and the show igmp traffic command to determine whether the device is receiving DVMRP traffic.
“This vulnerability results in memory exhaustion, which can impact other processes on the device. It is possible to recover the memory consumed by the IGMP process by restarting the IGMP process with the process restart igmp command,” the company notes.
There are no workarounds to address the issue, but Cisco has published information on various mitigations that customers can apply to remain protected.
Mitigation steps for the vulnerabilities include implementing a rate limiter for the IGMP traffic, which increases the time needed for a successful exploitation, along with implementing an access control entry (ACE) to an existing interface access control list (ACL).
Tracked as CVE-2020-3566, the flaw has a CVSS score of 8.6. Cisco reveals that attackers are already attempting to exploit the vulnerability.
Multiple iterations of ASR 9000 series aggregation services routers and IOS XR are affected. Cisco will release a software update to patch the bug but did not provide a timeframe for when that might happen.
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