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Fencer Intel
medium 4.3

CVE-2020-3449 json

Cisco IOS XR Software Additional Paths Denial of Service Vulnerability

published 6y ago modified 4mo ago also EUVD-2020-24720

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 64%
public exploits
0
none known

Summary

A vulnerability in the Border Gateway Protocol (BGP) additional paths feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to prevent authorized users from monitoring the BGP status and cause the BGP process to stop processing new updates, resulting in a denial of service (DOS) condition. The vulnerability is due to an incorrect calculation of lexicographical order when displaying additional path information within Cisco IOS XR Software, which causes an infinite loop. An attacker could exploit this vulnerability by sending a specific BGP update from a BGP neighbor peer session of an affected device; an authorized user must then issue a show bgp command for the vulnerability to be exploited. A successful exploit could allow the attacker to prevent authorized users from properly monitoring the BGP status and prevent BGP from processing new updates, resulting in outdated information in the routing and forwarding tables.

Patch / fix

  • cisco ios_xr 7.1.2, 7.2.1, 7.3.1

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

1.06% chance of exploitation in the next 30 days, higher than 64% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
NVD 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:N/A:P

Affected products

  • Cisco Cisco IOS XR Software

Classification

Weakness
  • CWE-754 Improper Check for Unusual or Exceptional Conditions
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.