CVE-2013-5479 in IOS
Summary
by MITRE
The DNS-over-TCP implementation in Cisco IOS 12.2 and 15.0 through 15.3, when NAT is used, allows remote attackers to cause a denial of service (device reload) via a crafted IPv4 DNS TCP stream, aka Bug ID CSCtn53730.
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Analysis
by VulDB Data Team • 05/25/2021
The vulnerability described in CVE-2013-5479 represents a critical denial of service flaw within Cisco IOS operating systems that affects versions 12.2 and 15.0 through 15.3. This issue specifically targets the DNS-over-TCP implementation when Network Address Translation is active within the network infrastructure. The vulnerability manifests when a remote attacker crafts a malicious IPv4 DNS TCP stream that triggers an unexpected device behavior leading to a complete system reload. This type of vulnerability falls under the category of improper handling of malformed input data, which aligns with CWE-129, indicating a weakness in input validation where the system fails to properly process or reject malformed network traffic. The attack vector specifically exploits the interaction between DNS processing and NAT functionality, creating a scenario where legitimate network operations can be disrupted through carefully constructed malicious packets.
The technical exploitation of this vulnerability occurs through the manipulation of DNS TCP streams that traverse network devices running affected Cisco IOS versions. When NAT is configured on the device, the system's handling of DNS responses becomes particularly susceptible to the crafted malformed packets. The flaw stems from insufficient validation of incoming DNS TCP data streams, particularly when these streams are processed in the context of NAT translation. This creates a condition where the device's TCP stack fails to properly handle the malformed data, leading to memory corruption or unexpected state transitions that ultimately result in the device performing an automatic reload. The vulnerability demonstrates how the combination of network protocol processing and address translation can create unexpected failure modes that are not adequately protected against by standard security measures. This behavior is consistent with ATT&CK technique T1499.001, which describes the use of resource exhaustion and system disruption methods to cause denial of service conditions.
The operational impact of CVE-2013-5479 extends beyond simple service interruption to potentially compromise entire network infrastructures that rely on affected Cisco devices. Network administrators may experience unexpected downtime as devices automatically reload, potentially disrupting critical services that depend on DNS resolution for network operations. The vulnerability's exploitation does not require authentication or specialized privileges, making it particularly dangerous as any remote attacker with network access can potentially trigger the denial of service condition. This creates significant risk for organizations where network availability is paramount, especially in environments where DNS servers are critical for internal operations and external connectivity. The automatic device reload creates a cascading effect that may impact multiple network services simultaneously, as the device becomes temporarily unavailable during the restart process. Organizations using affected Cisco IOS versions in production environments face potential business disruption and increased operational overhead due to the need for emergency patches and device maintenance. The vulnerability's presence in multiple IOS versions indicates a widespread issue that requires comprehensive remediation across affected network infrastructure. The lack of authentication requirements for exploitation means that the vulnerability can be leveraged by attackers without prior access to network credentials, increasing the attack surface and making the vulnerability particularly attractive for malicious actors seeking to disrupt network operations. This type of vulnerability also highlights the importance of network segmentation and monitoring, as the exploitation may not be immediately obvious to network administrators and could go undetected for extended periods.