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Medium severity5.5NVD Advisory· Published Nov 19, 2024· Updated May 12, 2026

CVE-2024-53042

CVE-2024-53042

Description

In the Linux kernel, the following vulnerability has been resolved:

ipv4: ip_tunnel: Fix suspicious RCU usage warning in ip_tunnel_init_flow()

There are code paths from which the function is called without holding the RCU read lock, resulting in a suspicious RCU usage warning [1].

Fix by using l3mdev_master_upper_ifindex_by_index() which will acquire the RCU read lock before calling l3mdev_master_upper_ifindex_by_index_rcu().

[1] WARNING: suspicious RCU usage 6.12.0-rc3-custom-gac8f72681cf2 #141 Not tainted ----------------------------- net/core/dev.c:876 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1 1 lock held by ip/361: #0: ffffffff86fc7cb0 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x377/0xf60

stack backtrace: CPU: 3 UID: 0 PID: 361 Comm: ip Not tainted 6.12.0-rc3-custom-gac8f72681cf2 #141 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 Call Trace:

dump_stack_lvl+0xba/0x110 lockdep_rcu_suspicious.cold+0x4f/0xd6 dev_get_by_index_rcu+0x1d3/0x210 l3mdev_master_upper_ifindex_by_index_rcu+0x2b/0xf0 ip_tunnel_bind_dev+0x72f/0xa00 ip_tunnel_newlink+0x368/0x7a0 ipgre_newlink+0x14c/0x170 __rtnl_newlink+0x1173/0x19c0 rtnl_newlink+0x6c/0xa0 rtnetlink_rcv_msg+0x3cc/0xf60 netlink_rcv_skb+0x171/0x450 netlink_unicast+0x539/0x7f0 netlink_sendmsg+0x8c1/0xd80 ____sys_sendmsg+0x8f9/0xc20 ___sys_sendmsg+0x197/0x1e0 __sys_sendmsg+0x122/0x1f0 do_syscall_64+0xbb/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

A suspicious RCU usage warning in the Linux kernel's ip_tunnel_init_flow() when creating tunnel interfaces without holding the RCU read lock is fixed by switching to a safer helper.

Vulnerability

Analysis

CVE-2024-53042 is a kernel vulnerability in the IPv4 tunnel implementation of the Linux kernel. The function ip_tunnel_init_flow() can be called from code paths that do not hold the RCU read lock, leading to a suspicious RCU usage warning. Specifically, when l3mdev_master_upper_ifindex_by_index_rcu() is invoked without RCU protection, the kernel triggers a warning because it traverses an RCU-protected list in a non-reader section [3].

Exploitation

Context

The issue is triggered during tunnel interface creation, for example when using ip tunnel add commands via netlink. The call stack shows that ip_tunnel_newlink() calls ip_tunnel_bind_dev(), which eventually leads to the RCU-suspicious path. The check shows that only the RTNL mutex is held at that point, not the RCU lock. No special privileges beyond the ability to create network tunnels are required; this is a local denial-of-service condition that can be triggered by unprivileged users in some configurations.

Impact

An attacker with the ability to create tunnel interfaces (e.g., via netlink) could trigger the RCU warning, leading to a kernel splat (stack trace printed to console) and potential system instability. The warning itself is a diagnostic mechanism, but repeated triggering could fill logs and potentially be leveraged in a denial-of-service scenario. The CVSS score is 5.5 (Medium), reflecting a local attack vector with low complexity and no authentication needed, but requiring low privileges.

Mitigation

The fix, committed in multiple stable kernel branches [4], replaces the direct call to l3mdev_master_upper_ifindex_by_index_rcu() with l3mdev_master_upper_ifindex_by_index(), which internally acquires the RCU read lock before calling the RCU variant. This ensures proper locking context. Users should apply the latest stable kernel updates from their distribution. The vulnerability is also noted in Siemens advisory SSA-265688 as affecting SIMATIC S7-1500 TM MFP - GNU/Linux subsystem [1].

References
  1. SSA-265688
  2. Making sure you're not a bot!
  3. Making sure you're not a bot!

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

84

Patches

0

No patches discovered yet.

Vulnerability mechanics

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References

9

News mentions

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