CVE-2022-49865 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
ipv6: addrlabel: fix infoleak when sending struct ifaddrlblmsg to network
When copying a `struct ifaddrlblmsg` to the network, __ifal_reserved remained uninitialized, resulting in a 1-byte infoleak:
BUG: KMSAN: kernel-network-infoleak in __netdev_start_xmit ./include/linux/netdevice.h:4841 __netdev_start_xmit ./include/linux/netdevice.h:4841 netdev_start_xmit ./include/linux/netdevice.h:4857 xmit_one net/core/dev.c:3590 dev_hard_start_xmit+0x1dc/0x800 net/core/dev.c:3606 __dev_queue_xmit+0x17e8/0x4350 net/core/dev.c:4256 dev_queue_xmit ./include/linux/netdevice.h:3009 __netlink_deliver_tap_skb net/netlink/af_netlink.c:307 __netlink_deliver_tap+0x728/0xad0 net/netlink/af_netlink.c:325 netlink_deliver_tap net/netlink/af_netlink.c:338 __netlink_sendskb net/netlink/af_netlink.c:1263 netlink_sendskb+0x1d9/0x200 net/netlink/af_netlink.c:1272 netlink_unicast+0x56d/0xf50 net/netlink/af_netlink.c:1360 nlmsg_unicast ./include/net/netlink.h:1061 rtnl_unicast+0x5a/0x80 net/core/rtnetlink.c:758 ip6addrlbl_get+0xfad/0x10f0 net/ipv6/addrlabel.c:628 rtnetlink_rcv_msg+0xb33/0x1570 net/core/rtnetlink.c:6082 ... Uninit was created at: slab_post_alloc_hook+0x118/0xb00 mm/slab.h:742 slab_alloc_node mm/slub.c:3398 __kmem_cache_alloc_node+0x4f2/0x930 mm/slub.c:3437 __do_kmalloc_node mm/slab_common.c:954 __kmalloc_node_track_caller+0x117/0x3d0 mm/slab_common.c:975 kmalloc_reserve net/core/skbuff.c:437 __alloc_skb+0x27a/0xab0 net/core/skbuff.c:509 alloc_skb ./include/linux/skbuff.h:1267 nlmsg_new ./include/net/netlink.h:964 ip6addrlbl_get+0x490/0x10f0 net/ipv6/addrlabel.c:608 rtnetlink_rcv_msg+0xb33/0x1570 net/core/rtnetlink.c:6082 netlink_rcv_skb+0x299/0x550 net/netlink/af_netlink.c:2540 rtnetlink_rcv+0x26/0x30 net/core/rtnetlink.c:6109 netlink_unicast_kernel net/netlink/af_netlink.c:1319 netlink_unicast+0x9ab/0xf50 net/netlink/af_netlink.c:1345 netlink_sendmsg+0xebc/0x10f0 net/netlink/af_netlink.c:1921 ...
This patch ensures that the reserved field is always initialized.
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Analysis
by VulDB Data Team • 03/14/2026
The vulnerability CVE-2022-49865 represents a kernel information leak in the Linux networking subsystem that specifically affects IPv6 address label handling. This issue occurs within the ipv6 subsystem when processing network messages related to address labels, creating a potential security risk through information disclosure. The flaw manifests in the `__ifal_reserved` field of the `struct ifaddrlblmsg` structure, which remains uninitialized during network transmission operations. This uninitialized memory content can inadvertently be exposed to network peers, potentially revealing sensitive kernel memory contents that could aid in further exploitation attempts.
The technical implementation of this vulnerability stems from improper memory initialization within the IPv6 address label processing code path. When the kernel prepares to send an `ifaddrlblmsg` structure over the network via the netlink interface, the reserved field that should be zeroed remains in an undefined state. This uninitialized byte contains whatever data was previously stored in that memory location, creating a 1-byte information leak that can be observed by network observers. The vulnerability is particularly concerning because it occurs during routine network operations and can be triggered through standard IPv6 address label management interfaces, making it accessible to both local and potentially remote attackers.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can provide attackers with insights into kernel memory layout and internal state information. According to CWE-248, this represents an uninitialized variable vulnerability that can lead to information exposure, while the ATT&CK framework would classify this under T1552.001 for exposure of information through uncontrolled data flow. The leak occurs during network transmission through the netlink communication mechanism, specifically when processing IPv6 address label requests. This vulnerability can be exploited by malicious actors to gather kernel memory contents that may contain sensitive information about system configuration, memory layout, or other potentially useful data for advanced exploitation techniques.
The patch addressing this vulnerability ensures that the reserved field within the `struct ifaddrlblmsg` structure is properly initialized before network transmission. This fix follows established security practices for preventing information leaks by ensuring all padding bytes and reserved fields are explicitly set to zero. The remediation aligns with security best practices outlined in the Linux kernel security documentation and follows the principle of least privilege by preventing unintended data exposure. Organizations should prioritize applying this patch as it addresses a fundamental memory management issue that could potentially be leveraged in combination with other vulnerabilities to gain additional system intelligence. The fix is minimal and focused, directly addressing the root cause without introducing significant performance impact or compatibility concerns in the networking subsystem.