CVE-1999-1341 in Linux
Summary
by MITRE
Linux kernel before 2.3.18 or 2.2.13pre15, with SLIP and PPP options, allows local unprivileged users to forge IP packets via the TIOCSETD option on tty devices.
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Analysis
by VulDB Data Team • 04/19/2026
This vulnerability exists in linux kernel versions prior to 2.3.18 and 2.2.13pre15 when slip and ppp options are enabled. The flaw resides in the terminal ioctl interface where the TIOCSETD option permits unprivileged local users to manipulate tty device drivers in ways that can result in forged ip packets being transmitted across the network. The vulnerability stems from insufficient validation of the data passed to the tty driver through this ioctl call, allowing malicious users to manipulate the underlying network communication layer. This represents a significant security issue as it provides a pathway for local users to bypass normal network security controls and potentially launch attacks against other networked systems. The technical implementation involves the kernel's handling of terminal device operations where the TIOCSETD ioctl command is used to set the terminal driver, but lacks proper checks to prevent modification of network packet generation parameters. The vulnerability enables privilege escalation from local user to network attack capability through manipulation of low-level terminal interfaces.
The operational impact of this vulnerability extends beyond simple packet forging to encompass potential network reconnaissance and attack capabilities. An attacker could use this flaw to craft malicious packets that appear to originate from legitimate network addresses, potentially bypassing firewall rules and intrusion detection systems that rely on source address validation. The vulnerability affects systems using slip and ppp network protocols which were common in early linux implementations and remain relevant in embedded systems and specialized network applications. This flaw demonstrates a classic case of insufficient input validation at kernel level interfaces, where user-supplied data is not properly sanitized before being used to modify critical network parameters. The vulnerability also highlights the risks associated with legacy terminal driver implementations that do not adequately separate user access controls from network communication functions.
Mitigation strategies for this vulnerability require immediate kernel updates to versions 2.3.18 or 2.2.13pre15 and later where the issue has been addressed through proper input validation and access control enforcement. System administrators should disable unnecessary slip and ppp kernel options if these protocols are not actively required for network operations. The fix typically involves implementing proper validation of the TIOCSETD parameter values and ensuring that only privileged processes can modify terminal driver configurations that affect network communication. Additional defensive measures include monitoring for unusual network traffic patterns that might indicate packet forging activity and implementing network-based intrusion detection systems to detect malformed packets originating from affected systems. This vulnerability aligns with CWE-122 which describes insufficient validation of input data, and represents a technique that could be categorized under ATT&CK tactic TA0011 (lateral movement) and technique T1071.004 (application layer protocol). The vulnerability also demonstrates how improper access control in kernel interfaces can lead to privilege escalation and network-level attacks.