CVE-2018-12018 in Go Ethereum
Summary
by MITRE
The GetBlockHeadersMsg handler in the LES protocol implementation in Go Ethereum (aka geth) before 1.8.11 may lead to an access violation because of an integer signedness error for the array index, which allows attackers to launch a Denial of Service attack by sending a packet with a -1 query.Skip value. The vulnerable remote node would be crashed by such an attack immediately, aka the EPoD (Ethereum Packet of Death) issue.
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Analysis
by VulDB Data Team • 04/03/2023
The vulnerability identified as CVE-2018-12018 represents a critical denial of service weakness within the Ethereum blockchain implementation known as geth. This flaw exists in the Light Ethereum Subprotocol (LES) which is responsible for handling blockchain header requests and responses. The vulnerability stems from a fundamental programming error in how the GetBlockHeadersMsg handler processes incoming network packets, specifically when dealing with the query.Skip parameter that controls the number of blocks to skip during header retrieval operations. The issue manifests as an integer signedness error that occurs when processing a negative value for the skip parameter, creating a scenario where the system attempts to access memory locations using an invalid array index derived from this negative input value.
The technical exploitation of this vulnerability occurs through a carefully crafted network packet that contains a query.Skip value of -1, which is then processed by the vulnerable geth node's LES protocol implementation. When the system encounters this negative value, it fails to properly validate the input before using it as an array index, leading to an access violation that causes the targeted node to immediately crash and terminate its operation. This type of vulnerability is classified as a CWE-190: Integer Overflow or Wraparound, which falls under the broader category of CWE-758: Reliance on Undefined, Unspecified, or Implementation-Dependent Behavior, and specifically maps to CWE-129: Improper Validation of Array Index. The crash occurs because the system attempts to allocate or access memory using an invalid negative index, which triggers a segmentation fault or similar memory access violation that terminates the process.
From an operational perspective, this vulnerability enables attackers to execute a sophisticated denial of service attack against Ethereum nodes running vulnerable versions of geth software. The attack is particularly dangerous because it requires minimal resources to execute and can be performed against any node that has not been patched, making it a scalable threat to the Ethereum network's availability. The vulnerability impacts the broader Ethereum ecosystem by potentially allowing attackers to disrupt network connectivity, reduce the number of available nodes for transaction processing, and create network fragmentation that could affect the overall stability and performance of the blockchain infrastructure. This attack vector directly aligns with the ATT&CK technique T1499.004: Endpoint Denial of Service, specifically targeting the network availability aspect of blockchain node operations, and represents a significant threat to the resilience of the Ethereum network against coordinated attacks.
The mitigation strategy for this vulnerability involves upgrading to geth version 1.8.11 or later, which contains the necessary patch to properly validate the query.Skip parameter before using it as an array index. The fix implements proper input validation that checks for negative values and either rejects invalid packets or converts them to safe positive values before processing. Network administrators should also implement additional monitoring and intrusion detection systems to identify suspicious network traffic patterns that might indicate attempts to exploit this vulnerability. The vulnerability demonstrates the critical importance of input validation in network protocol implementations and highlights the need for comprehensive security testing of blockchain node software to prevent similar issues from occurring in other network protocols or components. Organizations running Ethereum nodes must ensure immediate patching to prevent exploitation and maintain network integrity against this specific form of endpoint denial of service attack.