CVE-2025-38525
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-08-16

Last updated on: 2025-11-18

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix irq-disabled in local_bh_enable() The rxrpc_assess_MTU_size() function calls down into the IP layer to find out the MTU size for a route. When accepting an incoming call, this is called from rxrpc_new_incoming_call() which holds interrupts disabled across the code that calls down to it. Unfortunately, the IP layer uses local_bh_enable() which, config dependent, throws a warning if IRQs are enabled: WARNING: CPU: 1 PID: 5544 at kernel/softirq.c:387 __local_bh_enable_ip+0x43/0xd0 ... RIP: 0010:__local_bh_enable_ip+0x43/0xd0 ... Call Trace: <TASK> rt_cache_route+0x7e/0xa0 rt_set_nexthop.isra.0+0x3b3/0x3f0 __mkroute_output+0x43a/0x460 ip_route_output_key_hash+0xf7/0x140 ip_route_output_flow+0x1b/0x90 rxrpc_assess_MTU_size.isra.0+0x2a0/0x590 rxrpc_new_incoming_peer+0x46/0x120 rxrpc_alloc_incoming_call+0x1b1/0x400 rxrpc_new_incoming_call+0x1da/0x5e0 rxrpc_input_packet+0x827/0x900 rxrpc_io_thread+0x403/0xb60 kthread+0x2f7/0x310 ret_from_fork+0x2a/0x230 ret_from_fork_asm+0x1a/0x30 ... hardirqs last enabled at (23): _raw_spin_unlock_irq+0x24/0x50 hardirqs last disabled at (24): _raw_read_lock_irq+0x17/0x70 softirqs last enabled at (0): copy_process+0xc61/0x2730 softirqs last disabled at (25): rt_add_uncached_list+0x3c/0x90 Fix this by moving the call to rxrpc_assess_MTU_size() out of rxrpc_init_peer() and further up the stack where it can be done without interrupts disabled. It shouldn't be a problem for rxrpc_new_incoming_call() to do it after the locks are dropped as pmtud is going to be performed by the I/O thread - and we're in the I/O thread at this point.
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Meta Information
Published
2025-08-16
Last Modified
2025-11-18
Generated
2026-05-27
AI Q&A
2025-08-16
EPSS Evaluated
2026-05-25
NVD
CVE-2025-38525
Affected Vendors & Products
Showing 7 associated CPEs
Vendor Product Version / Range
linux linux_kernel 6.16
linux linux_kernel 6.16
linux linux_kernel 6.16
linux linux_kernel 6.16
linux linux_kernel 6.16
linux linux_kernel 6.16
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
Helpful Resources
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CWE ID Description
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability involves the Linux kernel's rxrpc component where the function rxrpc_assess_MTU_size() is called while interrupts are disabled. This function calls into the IP layer, which uses local_bh_enable(), a function that can cause warnings or issues if interrupts are enabled during its execution. The problem arises because rxrpc_new_incoming_call() holds interrupts disabled when calling rxrpc_assess_MTU_size(), leading to improper handling of interrupts and potential kernel warnings or instability. The fix moves the call to rxrpc_assess_MTU_size() to a point where interrupts are not disabled, preventing these issues.


How can this vulnerability impact me? :

This vulnerability can cause kernel warnings and potentially lead to instability or unexpected behavior in the Linux kernel's rxrpc networking component. Since it involves improper handling of interrupts, it could affect system reliability or performance during incoming network calls handled by rxrpc, possibly leading to degraded service or kernel errors.


How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring kernel logs for warnings related to irq-disabled in local_bh_enable(), specifically messages like: "WARNING: CPU: ... at kernel/softirq.c:387 __local_bh_enable_ip". You can check the kernel log using commands such as 'dmesg | grep local_bh_enable' or 'journalctl -k | grep local_bh_enable' to find relevant warnings indicating the issue.


What immediate steps should I take to mitigate this vulnerability?

Immediate mitigation involves updating the Linux kernel to a version where the fix has been applied. The fix moves the call to rxrpc_assess_MTU_size() out of rxrpc_init_peer() and further up the stack to avoid calling it with interrupts disabled. Until the update is applied, monitoring for the warning messages and avoiding workloads that trigger this code path may reduce risk.


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