CVE-2017-7477 in Linux
Summary
by MITRE
Heap-based buffer overflow in drivers/net/macsec.c in the MACsec module in the Linux kernel through 4.10.12 allows attackers to cause a denial of service or possibly have unspecified other impact by leveraging the use of a MAX_SKB_FRAGS+1 size in conjunction with the NETIF_F_FRAGLIST feature, leading to an error in the skb_to_sgvec function.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2017-7477 represents a critical heap-based buffer overflow within the MACsec module of the Linux kernel version 4.10.12 and earlier. This flaw resides in the drivers/net/macsec.c file and specifically targets the handling of network packet processing within the kernel's networking stack. The MACsec module implements IEEE 802.1AE MAC Security, which provides data confidentiality, integrity, and authentication for network traffic at the data link layer. The vulnerability arises from improper bounds checking when processing packets that utilize the NETIF_F_FRAGLIST feature, which enables fragmentation of network packets across multiple scatter-gather list entries. When an attacker crafts malicious network traffic that triggers this specific code path, the system becomes vulnerable to exploitation through memory corruption.
The technical implementation of this vulnerability involves a specific condition where a buffer overflow occurs when the kernel processes packets with a size exceeding MAX_SKB_FRAGS+1 elements while the NETIF_F_FRAGLIST feature is active. The skb_to_sgvec function, which converts socket buffer fragments into scatter-gather vector entries, fails to properly validate the number of fragments against the allocated buffer space. This mismatch creates a situation where memory beyond the intended buffer boundaries gets overwritten, potentially leading to arbitrary code execution or system instability. The flaw demonstrates characteristics consistent with CWE-121, heap-based buffer overflow, where insufficient bounds checking allows data to be written beyond allocated heap memory regions. The vulnerability's exploitation requires careful crafting of network packets that trigger the specific combination of conditions, making it less trivial to exploit but still highly concerning due to its potential for system compromise.
The operational impact of CVE-2017-7477 extends beyond simple denial of service, as it represents a potential pathway for privilege escalation and system compromise within kernel space. When successfully exploited, the buffer overflow could allow attackers to execute arbitrary code with kernel privileges, effectively bypassing user-space protections and potentially leading to complete system compromise. The vulnerability affects systems running Linux kernel versions up to 4.10.12, which includes numerous enterprise and server deployments where MACsec functionality is actively used for network security. The impact is particularly severe in environments where MACsec is enabled for securing critical network communications, as attackers could leverage this vulnerability to gain unauthorized access to sensitive network traffic or disrupt network operations. Network administrators must consider that exploitation could occur without requiring local access, making this a remote attack vector that could affect systems in production environments.
Mitigation strategies for CVE-2017-7477 primarily involve upgrading to patched kernel versions where the vulnerability has been addressed through proper bounds checking in the skb_to_sgvec function. The Linux kernel security team released patches that correct the buffer overflow by implementing proper validation of fragment counts against allocated buffer sizes, preventing the overflow condition from occurring. Organizations should prioritize patching their kernel versions to ensure protection against this vulnerability, particularly in environments where MACsec is actively deployed. Additional mitigations include network segmentation and monitoring for suspicious traffic patterns that might indicate exploitation attempts, as well as implementing network access controls to limit exposure to potentially malicious traffic. The vulnerability's characteristics align with ATT&CK technique T1068, exploit for privilege escalation, and T1499, network denial of service, making it a significant concern for cybersecurity teams implementing defense-in-depth strategies. System administrators should also consider implementing kernel hardening measures and monitoring for anomalous network behavior that could indicate exploitation attempts.