CVE-2002-1024 in IOS
Summary
by MITRE
Cisco IOS 12.0 through 12.2, when supporting SSH, allows remote attackers to cause a denial of service (CPU consumption) via a large packet that was designed to exploit the SSH CRC32 attack detection overflow (CVE-2001-0144).
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Analysis
by VulDB Data Team • 09/10/2025
The vulnerability described in CVE-2002-1024 represents a critical denial of service flaw affecting Cisco IOS versions 12.0 through 12.2 when operating with SSH protocol support. This issue stems from an inadequate handling of packet processing within the SSH implementation that specifically targets the CRC32 attack detection mechanism. The vulnerability manifests when remote attackers craft and transmit specially designed large packets that exploit a buffer overflow condition in the SSH CRC32 validation process. This particular weakness is directly related to CVE-2001-0144 which established the foundational understanding of the CRC32 attack detection overflow that enables this denial of service scenario.
The technical exploitation of this vulnerability occurs through the manipulation of SSH packet structures that trigger an overflow condition in the CRC32 validation routine. When the Cisco IOS device receives these malformed packets, the system attempts to process the cryptographic checksum validation with insufficient bounds checking, leading to excessive CPU utilization as the system becomes trapped in an infinite loop or memory corruption state. The flaw operates at the protocol processing layer where SSH packets are parsed and validated, specifically targeting the cryptographic integrity checking mechanism that should normally provide security against packet tampering but instead becomes a vector for resource exhaustion.
From an operational impact perspective, this vulnerability presents a significant risk to network availability and system stability. The denial of service condition causes continuous high CPU consumption that can render the affected Cisco IOS device unusable for legitimate network operations, effectively disabling SSH access and potentially disrupting critical network services that depend on the device's functionality. Network administrators may observe system performance degradation, increased system load, and complete service unavailability until the affected device is restarted or the vulnerable configuration is modified. The impact extends beyond simple service disruption as it can affect network management operations, remote access capabilities, and overall network infrastructure reliability.
The vulnerability aligns with CWE-129, which addresses improper validation of length parameters, and demonstrates characteristics consistent with CWE-770, concerning allocation of resources without limits or appropriate checks. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and represents a classic example of resource exhaustion attacks that target protocol implementation weaknesses. The attack vector operates over the network interface where SSH services are enabled, requiring no authentication to exploit, making it particularly dangerous in environments where SSH access is enabled on network devices. Mitigation strategies include implementing proper input validation, applying Cisco IOS patches, disabling SSH services when not required, and configuring rate limiting or packet filtering rules to prevent the exploitation of malformed SSH packets. Network segmentation and monitoring systems should also be deployed to detect unusual CPU utilization patterns that may indicate exploitation attempts.