CVE-2025-71093 in Linux
Summary
by MITRE • 01/13/2026
In the Linux kernel, the following vulnerability has been resolved:
e1000: fix OOB in e1000_tbi_should_accept()
In e1000_tbi_should_accept() we read the last byte of the frame via 'data[length - 1]' to evaluate the TBI workaround. If the descriptor-
reported length is zero or larger than the actual RX buffer size, this read goes out of bounds and can hit unrelated slab objects. The issue is observed from the NAPI receive path (e1000_clean_rx_irq):
================================================================== BUG: KASAN: slab-out-of-bounds in e1000_tbi_should_accept+0x610/0x790 Read of size 1 at addr ffff888014114e54 by task sshd/363
CPU: 0 PID: 363 Comm: sshd Not tainted 5.18.0-rc1 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0x5a/0x74 print_address_description+0x7b/0x440 print_report+0x101/0x200 kasan_report+0xc1/0xf0 e1000_tbi_should_accept+0x610/0x790 e1000_clean_rx_irq+0xa8c/0x1110 e1000_clean+0xde2/0x3c10 __napi_poll+0x98/0x380 net_rx_action+0x491/0xa20 __do_softirq+0x2c9/0x61d do_softirq+0xd1/0x120 </IRQ> <TASK> __local_bh_enable_ip+0xfe/0x130 ip_finish_output2+0x7d5/0xb00 __ip_queue_xmit+0xe24/0x1ab0 __tcp_transmit_skb+0x1bcb/0x3340 tcp_write_xmit+0x175d/0x6bd0 __tcp_push_pending_frames+0x7b/0x280 tcp_sendmsg_locked+0x2e4f/0x32d0 tcp_sendmsg+0x24/0x40 sock_write_iter+0x322/0x430 vfs_write+0x56c/0xa60 ksys_write+0xd1/0x190 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f511b476b10 Code: 73 01 c3 48 8b 0d 88 d3 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d f9 2b 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 8e 9b 01 00 48 89 04 24 RSP: 002b:00007ffc9211d4e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000004024 RCX: 00007f511b476b10 RDX: 0000000000004024 RSI: 0000559a9385962c RDI: 0000000000000003 RBP: 0000559a9383a400 R08: fffffffffffffff0 R09: 0000000000004f00 R10: 0000000000000070 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffc9211d57f R14: 0000559a9347bde7 R15: 0000000000000003 </TASK> Allocated by task 1: __kasan_krealloc+0x131/0x1c0 krealloc+0x90/0xc0 add_sysfs_param+0xcb/0x8a0 kernel_add_sysfs_param+0x81/0xd4 param_sysfs_builtin+0x138/0x1a6 param_sysfs_init+0x57/0x5b do_one_initcall+0x104/0x250 do_initcall_level+0x102/0x132 do_initcalls+0x46/0x74 kernel_init_freeable+0x28f/0x393 kernel_init+0x14/0x1a0 ret_from_fork+0x22/0x30 The buggy address belongs to the object at ffff888014114000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 1620 bytes to the right of 2048-byte region [ffff888014114000, ffff888014114800]
The buggy address belongs to the physical page: page:ffffea0000504400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14110 head:ffffea0000504400 order:3 compound_mapcount:0 compound_pincount:0 flags: 0x100000000010200(slab|head|node=0|zone=1) raw: 0100000000010200 0000000000000000 dead000000000001 ffff888013442000 raw: 0000000000000000 0000000000080008 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected ==================================================================
This happens because the TBI check unconditionally dereferences the last byte without validating the reported length first:
u8 last_byte = *(data + length - 1);
Fix by rejecting the frame early if the length is zero, or if it exceeds adapter->rx_buffer_len. This preserves the TBI workaround semantics for valid frames and prevents touching memory beyond the RX buffer.
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Analysis
by VulDB Data Team • 03/31/2026
The vulnerability described in CVE-2025-71093 affects the Linux kernel's e1000 network driver, specifically within the e1000_tbi_should_accept() function. This flaw constitutes a buffer overflow condition that arises when processing received network frames, creating a potential security risk for systems utilizing the affected network hardware. The issue manifests when the driver attempts to read the last byte of a received frame to evaluate a TBI (Ten Bit Interface) workaround, without first validating the descriptor-reported frame length against the actual RX buffer size. This validation gap enables an out-of-bounds memory access that can result in corruption of adjacent memory regions or information disclosure.
The technical flaw occurs in the NAPI receive path, specifically within the e1000_clean_rx_irq function, where the driver reads from memory location data + length - 1 without proper bounds checking. When the reported frame length is either zero or exceeds the allocated RX buffer size, this read operation accesses memory beyond the intended buffer boundaries. The kernel's KASAN (Kernel Address Sanitizer) detects this violation, indicating that the access occurs at address ffff888014114e54, which belongs to a kmalloc-2k slab object. This out-of-bounds read can potentially overwrite unrelated slab objects, leading to memory corruption that may be exploited to cause system instability or potentially achieve privilege escalation.
The operational impact of this vulnerability extends beyond simple memory corruption, as it represents a classic buffer over-read condition that aligns with CWE-125 - "Out-of-bounds Read" and may be leveraged for privilege escalation or denial of service attacks. The attack vector requires an attacker to control or influence the network traffic received by a vulnerable system, which can be achieved through network-based attacks or by compromising a system with network access. This vulnerability is particularly concerning in environments where untrusted network traffic is processed, as it could be exploited to gain unauthorized access to system resources or cause system crashes. The flaw affects systems running Linux kernel versions that include the e1000 driver and is especially relevant in virtualized environments where QEMU-based systems are common, as evidenced by the crash trace showing QEMU hardware identification.
Mitigation of this vulnerability requires implementing proper bounds checking in the e1000_tbi_should_accept() function to validate the frame length before attempting to read the last byte of the frame. The fix involves rejecting frames early when the length is zero or exceeds the adapter's rx_buffer_len, which preserves the intended TBI workaround semantics for valid frames while preventing out-of-bounds memory access. This approach aligns with the principle of input validation and defensive programming, ensuring that all memory accesses are bounded and within the allocated memory regions. System administrators should update their Linux kernel versions to include the patched driver, and organizations should monitor for any signs of exploitation attempts through network traffic analysis or system monitoring tools. The vulnerability also highlights the importance of kernel security hardening measures and regular security updates to protect against similar memory corruption flaws in network drivers and other kernel subsystems.