Exploited vulnerability · CISA KEV

Is CVE-2020-3566 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Cisco IOS XR · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2020-3566, Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 431 days after it was published. It affects Cisco IOS XR. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 3 Nov 2021

ransomwareNot knownno confirmed use

EPSSbelow top 10%lower predicted activity right now (it is still confirmed exploited)

severity8.6CVSS 3.1 · high

US federal due3 May 2022BOD 22-01 deadline

What it is

Cisco IOS XR Distance Vector Multicast Routing Protocol (DVMRP) incorrectly handles Internet Group Management Protocol (IGMP) packets. Exploitation could allow an unauthenticated, remote attacker to immediately crash the IGMP process or make it consume available memory and eventually crash.

Vendor	Cisco (103 exploited CVEs in KEV)
Product	IOS XR
Vulnerability	Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability
Weakness	CWE-400
Published	29 Aug 2020
Added to KEV	3 Nov 2021
Reported by (CNA)	cisco

What to do

Check whether you run it. Look for IOS XR in your asset inventory, including appliances and cloud images. Stack check lists every exploited Cisco CVE at once.
Apply the fix. Apply updates per vendor instructions.
If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 29 Aug 2020.
Get told next time. Email alerts when CISA adds a CVE for Cisco.

Other exploited CVEs in IOS XR

CVE-2022-20821: Cisco IOS XR Open Port Vulnerability (23 May 2022)
CVE-2010-3035: Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability (25 Mar 2022)
CVE-2009-2055: Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability (25 Mar 2022)
CVE-2020-3118: Cisco IOS XR Software Discovery Protocol Format String Vulnerability (3 Nov 2021)
CVE-2020-3569: Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability (3 Nov 2021)

References

nvd.nist.gov/vuln/detail/CVE-2020-3566

Questions

Is CVE-2020-3566 being exploited?

Yes. CISA added CVE-2020-3566 to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, which means there is reliable evidence of exploitation in the wild.

Is CVE-2020-3566 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2020-3566?

Apply updates per vendor instructions. Check Cisco's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected IOS XR and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2021 · Cisco scorecard · act-now radar.

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