Researchers found DoS flaws in popular BGP implementation

Vulnerabilities in a software implementation of the Border Gateway Protocol (BGP) that could be weaponized to trigger a DoS condition on BGP peers.

Forescout Vedere Labs researchers discovered multiple vulnerabilities in the software implementation of the Border Gateway Protocol (BGP). The issues reside in the BGP message parsing in version 8.4 of FRRouting implementation, a leading open-source implementation of the protocol. The flaw can be exploited to trigger a denial of service (DoS) condition on vulnerable BGP peers.

Technically the flaws can be exploited to drop all BGP sessions and routing tables, rendering the peer unresponsive.

The researchers pointed out that Border Gateway Protocol implementations are widely adopted, common uses include traffic routing in large data centers and BGP extensions, such as MP-BGP, or for MPLS L3 VPNs.

The FRRouting implementation is currently used in the networking solutions of several major vendors, including nVidia Cumulus, DENT, and SONiC.

“Attackers may leverage any of the three new vulnerabilities to achieve a DoS on a vulnerable BGP peer, thus dropping all BGP sessions and routing tables and rendering the peer unresponsive for several seconds. The DoS condition may be prolonged indefinitely by repeatedly sending malformed packets.” reads the advisory published by the company.

The discovery is the result of a broader analysis of seven popular Border Gateway Protocol implementations, three open-source (FRRouting, BIRD, OpenBGPd) and four closed source (Mikrotik RouterOS, Juniper JunOS, Cisco IOS, Arista EOS).

Below is the list of the flaws discovered by Forescout:

CVE ID	Description	CVSSv3.1	Potential Impact
CVE-2022-40302	Out-of-bounds read when processing a malformed BGP OPEN message with an Extended Optional Parameters Length option.	6.5	DoS
CVE-2022-40318	Out-of-bounds read when processing a malformed BGP OPEN message with an Extended Optional Parameters Length option. This is a different issue from CVE-2022-40302.	6.5	DoS
CVE-2022-43681	Out-of-bounds read when processing a malformed BGP OPEN message that abruptly ends with the option length octet (or the option length word, in case of OPEN with extended option lengths message).	6.5	DoS

The researchers pointed out that the flaws CVE-2022-40302 and CVE-2022-43681 can be triggered before FRRouting validates BGP Identifier and ASN fields. While FRRouting only allows connections between configured peers by default (e.g., OPEN messages from hosts not present in the config files will not be accepted), in the attack scenario described in the advisory, threat actors can spoof a valid IP address of a trusted peer. Threat actors can also take advantage of misconfigurations or attempt to compromise a legitimate peer by exploiting other vulnerabilities.

It has been estimated that there are over 330,000 hosts with BGP enabled on the internet and approximately 1,000 of them replies to unsolicited BGP OPEN messages. Most of the Border Gateway Protocol hosts are in China (close to 100,000), the US (50,000) and the UK (16,000). The experts discovered more than 1,000 hosts running FRRouting, but not all of them have Border Gateway Protocol enabled. Again.

The vulnerabilities were addressed by the FRRouting team with the release of the following versions:

CVE-2022-40302 and CVE-2022-40318: https://github.com/FRRouting/frr/pull/12043
CVE-2022-43681: https://github.com/FRRouting/frr/pull/12247

“Our research shows that modern BGP implementations still have low-hanging fruit that can be abused by attackers.” concludes the advisory.

Forescout also released a Python-based open-source fuzzer tool that allows organizations to test the security of the Border Gateway Protocol suites used internally and find new vulnerabilities in Border Gateway Protocol implementations.

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Pierluigi Paganini

(SecurityAffairs – hacking, Border Gateway Protocol)

Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.