CVE-2025-39903 Affecting kernel-rt-debug-devel package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-devel package and not the kernel-rt-debug-devel package as distributed by RHEL. See How to fix? for RHEL:10 relevant fixed versions and status.

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

of_numa: fix uninitialized memory nodes causing kernel panic

When there are memory-only nodes (nodes without CPUs), these nodes are not properly initialized, causing kernel panic during boot.

of_numa_init of_numa_parse_cpu_nodes node_set(nid, numa_nodes_parsed); of_numa_parse_memory_nodes

In of_numa_parse_cpu_nodes, numa_nodes_parsed gets updated only for nodes containing CPUs. Memory-only nodes should have been updated in of_numa_parse_memory_nodes, but they weren't.

Subsequently, when free_area_init() attempts to access NODE_DATA() for these uninitialized memory nodes, the kernel panics due to NULL pointer dereference.

This can be reproduced on ARM64 QEMU with 1 CPU and 2 memory nodes:

qemu-system-aarch64
-cpu host -nographic
-m 4G -smp 1
-machine virt,accel=kvm,gic-version=3,iommu=smmuv3
-object memory-backend-ram,size=2G,id=mem0
-object memory-backend-ram,size=2G,id=mem1
-numa node,nodeid=0,memdev=mem0
-numa node,nodeid=1,memdev=mem1
-kernel $IMAGE
-hda $DISK
-append "console=ttyAMA0 root=/dev/vda rw earlycon"

[ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x481fd010] [ 0.000000] Linux version 6.17.0-rc1-00001-gabb4b3daf18c-dirty (yintirui@local) (gcc (GCC) 12.3.1, GNU ld (GNU Binutils) 2.41) #52 SMP PREEMPT Mon Aug 18 09:49:40 CST 2025 [ 0.000000] KASLR enabled [ 0.000000] random: crng init done [ 0.000000] Machine model: linux,dummy-virt [ 0.000000] efi: UEFI not found. [ 0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '') [ 0.000000] printk: legacy bootconsole [pl11] enabled [ 0.000000] OF: reserved mem: Reserved memory: No reserved-memory node in the DT [ 0.000000] NODE_DATA(0) allocated [mem 0xbfffd9c0-0xbfffffff] [ 0.000000] node 1 must be removed before remove section 23 [ 0.000000] Zone ranges: [ 0.000000] DMA [mem 0x0000000040000000-0x00000000ffffffff] [ 0.000000] DMA32 empty [ 0.000000] Normal [mem 0x0000000100000000-0x000000013fffffff] [ 0.000000] Movable zone start for each node [ 0.000000] Early memory node ranges [ 0.000000] node 0: [mem 0x0000000040000000-0x00000000bfffffff] [ 0.000000] node 1: [mem 0x00000000c0000000-0x000000013fffffff] [ 0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x00000000bfffffff] [ 0.000000] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a0 [ 0.000000] Mem abort info: [ 0.000000] ESR = 0x0000000096000004 [ 0.000000] EC = 0x25: DABT (current EL), IL = 32 bits [ 0.000000] SET = 0, FnV = 0 [ 0.000000] EA = 0, S1PTW = 0 [ 0.000000] FSC = 0x04: level 0 translation fault [ 0.000000] Data abort info: [ 0.000000] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 [ 0.000000] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 0.000000] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 0.000000] [00000000000000a0] user address but active_mm is swapper [ 0.000000] Internal error: Oops: 0000000096000004 [#1] SMP [ 0.000000] Modules linked in: [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.17.0-rc1-00001-g760c6dabf762-dirty #54 PREEMPT [ 0.000000] Hardware name: linux,dummy-virt (DT) [ 0.000000] pstate: 800000c5 (Nzcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 0.000000] pc : free_area_init+0x50c/0xf9c [ 0.000000] lr : free_area_init+0x5c0/0xf9c [ 0.000000] sp : ffffa02ca0f33c00 [ 0.000000] x29: ffffa02ca0f33cb0 x28: 0000000000000000 x27: 0000000000000000 [ 0.000000] x26: 4ec4ec4ec4ec4ec5 x25: 00000000000c0000 x24: 00000000000c0000 [ 0.000000] x23: 0000000000040000 x22: 0000000000000000 x21: ffffa02ca0f3b368 [ 0.000000] x20: ffffa02ca14c7b98 x19: 0000000000000000 x18: 0000000000000002 [ 0.000000] x17: 000000000000cacc x16: 0000000000000001 x15: 0000000000000001 [ 0.000000] x14: 0000000080000000 x13: 0000000000000018 x12: 0000000000000002 [ 0.0 ---truncated---

• https://bugzilla.redhat.com/show_bug.cgi?id=2400593
• https://access.redhat.com/security/cve/CVE-2025-39903
• https://git.kernel.org/stable/c/c2daa6eb4740720b5bd0e06267d7c93a3eed844e
• https://git.kernel.org/stable/c/ee4d098cbc9160f573b5c1b5a51d6158efdb2896
• https://git.kernel.org/stable/c/f3286ad8eeae15fd4bd5c12f9adfe888b26baf62