Cisco IOS XR BGP Unrecognized Transitive Attribute Handling Vulnerability (CVE-2010-3035) Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTCisco IOS XR software versions 3.4.0 through 3.9.1 with the Border Gateway Protocol (BGP) routing process enabled.
A remote attacker can trigger a denial of service (BGP peering session reset) by sending a specially crafted BGP prefix announcement, potentially disrupting global routing tables.
Apply the official Cisco Software Maintenance Upgrade (SMU) or upgrade to a non-vulnerable release of Cisco IOS XR.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
To permanently resolve the vulnerability, apply the specific Software Maintenance Upgrade (SMU) for your release or upgrade to IOS XR 3.9.2, 4.0.0, or later. Use the following commands to install the SMU on IOS XR:
# Verify current active packages and SMUs
show install active summary
# Add and activate the SMU patch from a secure TFTP server
install add tftp://10.1.1.100/asr9k-px-3.9.1.CSCti62211.tar activate
# Commit the changes to make them persistent across reboots
install commit2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, secure your BGP sessions by implementing MD5 authentication and TTL security to prevent unauthorized peers from injecting malicious BGP updates.
# Hardening BGP neighbor configuration on Cisco IOS XR
router bgp 65001
neighbor 192.168.1.1
remote-as 65002
password encrypted 0822455D0A181C
ttl-security
address-family ipv4 unicast
route-policy BGP_INBOUND in
!
!
!3. Log Audit & IoC Verification Commands
Monitor the router logs for unexpected BGP session resets and verify the running software version to determine exposure.
# Search system logs for BGP notification and reset events
show logging | include 'BGP-3-NOTIFICATION'
# Check the current running version of Cisco IOS XR
show versionStop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2010-3035, Cisco Bug ID CSCti62211) exists in the BGP implementation of Cisco IOS XR. The root cause is the improper handling of unrecognized transitive attributes within BGP update messages. According to BGP specifications, unrecognized transitive attributes should be accepted and passed along to other peers. However, vulnerable versions of IOS XR fail to parse certain malformed or specific unrecognized transitive attributes correctly, leading to an internal parsing exception that tears down the active BGP session.
2. Exploitation Mechanics & Attack Scenario
An attacker can exploit this vulnerability by injecting a crafted BGP update message containing a specific unrecognized transitive attribute (such as attribute type code 99, which was observed in active wild exploits in August 2010). When the vulnerable IOS XR router receives this update from an adjacent peer or via propagation through the global BGP mesh, it encounters a parsing failure. The router then sends a BGP Notification message to its peer and terminates the TCP session. This causes route flapping, leading to severe packet loss and routing instability across the affected network segments.
3. Infrastructure & Business Impact
As a CISA KEV-listed vulnerability, this flaw has a proven history of active exploitation in production environments. For service providers and large enterprises, the disruption of core BGP peering sessions directly translates to widespread network outages, SLA breaches, and loss of critical business connectivity. The cascading effect of route re-calculations (flapping) can also exhaust CPU resources on neighboring transit routers.
Official Vendor Advisories & References
Cisco IOS XR 3.4.0 through 3.9.1, when BGP is enabled, does not properly handle unrecognized transitive attributes, which allows remote attackers to cause a denial of service (peering reset) via a crafted prefix announcement, as demonstrated in the wild in August 2010 with attribute type code 99, aka Bug ID CSCti62211.
Frequently Asked SecOps Questions (CVE-2010-3035)
FAQQ1. How critical is CVE-2010-3035 and is it actively exploited in the wild?
CVE-2010-3035 is rated CVSS 7.5 (HIGH) with a 30-day EPSS exploitation probability of 5.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2010-3035?
Primary impacted vendors include cisco across ios_xr. Scope summary: Cisco IOS XR versions 3.4.0 through 3.9.1 inclusive, where BGP routing is configured and active.
Q3. What temporary mitigations or workarounds exist for CVE-2010-3035 before patching?
[Mitigation] Apply the official Cisco Software Maintenance Upgrade (SMU) or upgrade to a non-vulnerable release of Cisco IOS XR. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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