CVE-2024-27414 in Linux
Summary
by MITRE • 05/17/2024
In the Linux kernel, the following vulnerability has been resolved:
rtnetlink: fix error logic of IFLA_BRIDGE_FLAGS writing back
In the commit d73ef2d69c0d ("rtnetlink: let rtnl_bridge_setlink checks IFLA_BRIDGE_MODE length"), an adjustment was made to the old loop logic in the function `rtnl_bridge_setlink` to enable the loop to also check the length of the IFLA_BRIDGE_MODE attribute. However, this adjustment removed the `break` statement and led to an error logic of the flags writing back at the end of this function.
if (have_flags) memcpy(nla_data(attr), &flags, sizeof(flags)); // attr should point to IFLA_BRIDGE_FLAGS NLA !!!
Before the mentioned commit, the `attr` is granted to be IFLA_BRIDGE_FLAGS. However, this is not necessarily true fow now as the updated loop will let the attr point to the last NLA, even an invalid NLA which could cause overflow writes.
This patch introduces a new variable `br_flag` to save the NLA pointer that points to IFLA_BRIDGE_FLAGS and uses it to resolve the mentioned error logic.
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Analysis
by VulDB Data Team • 12/17/2025
The vulnerability CVE-2024-27414 resides within the Linux kernel's rtnetlink subsystem, specifically in the `rtnl_bridge_setlink` function that handles bridge interface configuration operations. This issue represents a critical logic flaw that could enable unauthorized modification of network bridge parameters through malformed input data. The vulnerability stems from an improper handling of Netlink attribute pointers during the processing of bridge configuration requests, creating a potential vector for privilege escalation or network disruption attacks. The flaw was introduced during a previous commit that attempted to enhance validation of the IFLA_BRIDGE_MODE attribute length, inadvertently disrupting the proper flow of flag attribute handling. This demonstrates how seemingly benign code modifications can introduce serious security implications in kernel space operations.
The technical root cause involves a fundamental error in loop logic within the `rtnl_bridge_setlink` function where the attribute pointer `attr` no longer reliably points to the intended `IFLA_BRIDGE_FLAGS` Netlink attribute after the code modification. Previously, the code structure guaranteed that `attr` would reference the correct flag attribute, but the updated loop logic allows `attr` to potentially point to any of several processed attributes including invalid ones. When the function attempts to write back the bridge flags using `memcpy(nla_data(attr), &flags, sizeof(flags))`, it may write to memory locations that are not properly allocated for bridge flags, resulting in memory corruption. This error logic directly violates the expected behavior of Netlink attribute processing and creates a scenario where arbitrary memory locations could be overwritten, potentially leading to kernel crashes or more severe exploitation opportunities. The vulnerability aligns with CWE-787 (Out-of-bounds Write) and CWE-121 (Stack-based Buffer Overflow) classifications, as the improper pointer handling can lead to memory corruption through direct memory manipulation.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it represents a potential path for privilege escalation within the kernel space. An attacker who can craft malicious Netlink messages containing bridge configuration data could potentially exploit this flaw to overwrite critical kernel memory structures, leading to system instability or unauthorized privilege elevation. The vulnerability affects all Linux kernel versions that include the problematic commit, making it particularly concerning for systems running network bridge configurations or those that process bridge-related Netlink messages. Network administrators and security teams must understand that this vulnerability could be exploited in scenarios involving network management applications, container orchestration platforms, or any system that relies on bridge interface configuration through rtnetlink. The ATT&CK framework categorizes this as a privilege escalation technique under T1068 (Local Privilege Escalation) and potentially T1566 (Phishing for Information) if attackers use it to gain access to systems before escalating privileges. The vulnerability's exploitation potential is amplified by the fact that it operates at kernel level where memory corruption can be leveraged for more sophisticated attacks including code execution.
The recommended mitigation strategy involves applying the patch that introduces a dedicated variable `br_flag` to maintain the correct reference to the `IFLA_BRIDGE_FLAGS` Netlink attribute throughout the function execution. This approach ensures that the flag writing back operation always targets the correct memory location, preventing the out-of-bounds write condition that the vulnerability exploits. System administrators should prioritize updating their kernel versions to include the fix, particularly in environments where network bridge functionality is actively used or where systems may be exposed to untrusted network input. The patch implementation follows best practices for kernel security by maintaining explicit pointer validation and ensuring that attribute processing maintains its intended semantics. Organizations should also implement monitoring for unusual Netlink traffic patterns that might indicate exploitation attempts, as the vulnerability requires specific Netlink message construction to be effective. Regular kernel updates and security audits of network configuration systems will help prevent exploitation of this and similar vulnerabilities that could impact the stability and security of Linux-based network infrastructure.