CVE-2022-49623
Published: 26 February 2025
Summary
CVE-2022-49623 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 1.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2022-49623 is a slab-out-of-bounds read vulnerability in the Linux kernel's powerpc/xive/spapr component. KASAN detected invalid memory access beyond the end of the xibm->bitmap allocation during calls to _find_first_zero_bit in functions like xive_spapr_get_ipi and xive_setup_cpu_ipi. The issue stems from incorrect allocation sizing, using bit counts instead of the proper byte size (BITS_TO_LONGS(count) * sizeof(long)), which can result in allocations smaller than a long, leading to out-of-bounds reads, classified under CWE-125 with a CVSS v3.1 score of 7.1 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H).
A local attacker with low privileges can exploit this vulnerability during kernel initialization on affected powerpc systems, such as in pSeries_smp_probe and smp_prepare_cpus. Successful exploitation enables high-impact confidentiality violations by reading sensitive kernel memory and high-impact availability disruptions, potentially causing denial of service through crashes, without requiring user interaction.
Kernel patches in stable releases address the issue by replacing manual kmalloc with bitmap_zalloc() for proper allocation and zero-initialization of the IRQ bitmap, paired with bitmap_free() for deallocation. Relevant commits include 10f2cd373e65bcd3be8f3cdc71c330c25763dfd8, 19fc5bb93c6bbdce8292b4d7eed04e2fa118d2fe, and 99d1c36bddd93919072b5a51a89297bbb5ad6a6f, available via git.kernel.org.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2022-54609
Vulnerability details
In the Linux kernel, the following vulnerability has been resolved: powerpc/xive/spapr: correct bitmap allocation size kasan detects access beyond the end of the xibm->bitmap allocation: BUG: KASAN: slab-out-of-bounds in _find_first_zero_bit+0x40/0x140 Read of size 8 at addr c00000001d1d0118 by task swapper/0/1…
more
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.19.0-rc2-00001-g90df023b36dd #28 Call Trace: [c00000001d98f770] [c0000000012baab8] dump_stack_lvl+0xac/0x108 (unreliable) [c00000001d98f7b0] [c00000000068faac] print_report+0x37c/0x710 [c00000001d98f880] [c0000000006902c0] kasan_report+0x110/0x354 [c00000001d98f950] [c000000000692324] __asan_load8+0xa4/0xe0 [c00000001d98f970] [c0000000011c6ed0] _find_first_zero_bit+0x40/0x140 [c00000001d98f9b0] [c0000000000dbfbc] xive_spapr_get_ipi+0xcc/0x260 [c00000001d98fa70] [c0000000000d6d28] xive_setup_cpu_ipi+0x1e8/0x450 [c00000001d98fb30] [c000000004032a20] pSeries_smp_probe+0x5c/0x118 [c00000001d98fb60] [c000000004018b44] smp_prepare_cpus+0x944/0x9ac [c00000001d98fc90] [c000000004009f9c] kernel_init_freeable+0x2d4/0x640 [c00000001d98fd90] [c0000000000131e8] kernel_init+0x28/0x1d0 [c00000001d98fe10] [c00000000000cd54] ret_from_kernel_thread+0x5c/0x64 Allocated by task 0: kasan_save_stack+0x34/0x70 __kasan_kmalloc+0xb4/0xf0 __kmalloc+0x268/0x540 xive_spapr_init+0x4d0/0x77c pseries_init_irq+0x40/0x27c init_IRQ+0x44/0x84 start_kernel+0x2a4/0x538 start_here_common+0x1c/0x20 The buggy address belongs to the object at c00000001d1d0118 which belongs to the cache kmalloc-8 of size 8 The buggy address is located 0 bytes inside of 8-byte region [c00000001d1d0118, c00000001d1d0120) The buggy address belongs to the physical page: page:c00c000000074740 refcount:1 mapcount:0 mapping:0000000000000000 index:0xc00000001d1d0558 pfn:0x1d1d flags: 0x7ffff000000200(slab|node=0|zone=0|lastcpupid=0x7ffff) raw: 007ffff000000200 c00000001d0003c8 c00000001d0003c8 c00000001d010480 raw: c00000001d1d0558 0000000001e1000a 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: c00000001d1d0000: fc 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc c00000001d1d0080: fc fc 00 fc fc fc fc fc fc fc fc fc fc fc fc fc >c00000001d1d0100: fc fc fc 02 fc fc fc fc fc fc fc fc fc fc fc fc ^ c00000001d1d0180: fc fc fc fc 04 fc fc fc fc fc fc fc fc fc fc fc c00000001d1d0200: fc fc fc fc fc 04 fc fc fc fc fc fc fc fc fc fc This happens because the allocation uses the wrong unit (bits) when it should pass (BITS_TO_LONGS(count) * sizeof(long)) or equivalent. With small numbers of bits, the allocated object can be smaller than sizeof(long), which results in invalid accesses. Use bitmap_zalloc() to allocate and initialize the irq bitmap, paired with bitmap_free() for consistency.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
OOB kernel memory read directly enables local data access (T1005); resulting crashes enable targeted endpoint DoS via system exploitation (T1499.004).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires timely installation of kernel patches that correct the incorrect bitmap allocation size, directly eliminating the slab-out-of-bounds read vulnerability.
Implements memory protection mechanisms that enforce separation and prevent unauthorized kernel memory access, mitigating exploitation of out-of-bounds reads.
Enables vulnerability scanning to identify the specific Linux kernel slab-out-of-bounds issue (CVE-2022-49623), supporting proactive flaw remediation.