CVE-2025-71087: iavf: fix off-by-one issues in iavf_config_rss_reg()

Vulnerability summary

CVE-2025-71087 is a medium (CVSS 5.5) Off-by-one Error vulnerability in linux. EPSS estimates a 0.14% chance of exploitation in the next 30 days, higher than 3.1% of scored vulnerabilities.

Timeline

1. 13-01-2026
   PublishedVulnerability first disclosed.
2. 19-10-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: iavf: fix off-by-one issues in iavf_config_rss_reg() There are off-by-one bugs when configuring RSS hash key and lookup table, causing out-of-bounds reads to memory [1] and out-of-bounds writes to device registers. Before commit 43a3d9ba34c9 ("i40evf: Allow PF driver to configure RSS"), the loop upper bounds were: i <= I40E_VFQF_{HKEY,HLUT}_MAX_INDEX which is safe since the value is the last valid index. That commit changed the bounds to: i <= adapter->rss_{key,lut}_size / 4 where `rss_{key,lut}_size / 4` is the number of dwords, so the last valid index is `(rss_{key,lut}_size / 4) - 1`. Therefore, using `<=` accesses one element past the end. Fix the issues by using `<` instead of `<=`, ensuring we do not exceed the bounds. [1] KASAN splat about rss_key_size off-by-one BUG: KASAN: slab-out-of-bounds in iavf_config_rss+0x619/0x800 Read of size 4 at addr ffff888102c50134 by task kworker/u8:6/63 CPU: 0 UID: 0 PID: 63 Comm: kworker/u8:6 Not tainted 6.18.0-rc2-enjuk-tnguy-00378-g3005f5b77652-dirty #156 PREEMPT(voluntary) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: iavf iavf_watchdog_task Call Trace: <TASK> dump_stack_lvl+0x6f/0xb0 print_report+0x170/0x4f3 kasan_report+0xe1/0x1a0 iavf_config_rss+0x619/0x800 iavf_watchdog_task+0x2be7/0x3230 process_one_work+0x7fd/0x1420 worker_thread+0x4d1/0xd40 kthread+0x344/0x660 ret_from_fork+0x249/0x320 ret_from_fork_asm+0x1a/0x30 </TASK> Allocated by task 63: kasan_save_stack+0x30/0x50 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x7f/0x90 __kmalloc_noprof+0x246/0x6f0 iavf_watchdog_task+0x28fc/0x3230 process_one_work+0x7fd/0x1420 worker_thread+0x4d1/0xd40 kthread+0x344/0x660 ret_from_fork+0x249/0x320 ret_from_fork_asm+0x1a/0x30 The buggy address belongs to the object at ffff888102c50100 which belongs to the cache kmalloc-64 of size 64 The buggy address is located 0 bytes to the right of allocated 52-byte region [ffff888102c50100, ffff888102c50134) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x102c50 flags: 0x200000000000000(node=0|zone=2) page_type: f5(slab) raw: 0200000000000000 ffff8881000418c0 dead000000000122 0000000000000000 raw: 0000000000000000 0000000080200020 00000000f5000000 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888102c50000: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc ffff888102c50080: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc >ffff888102c50100: 00 00 00 00 00 00 04 fc fc fc fc fc fc fc fc fc ^ ffff888102c50180: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc ffff888102c50200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

• CWE-193Off-by-one ErrorA product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.