CVE-2025-38713 in Linux
Summary
by MITRE • 09/04/2025
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: fix slab-out-of-bounds read in hfsplus_uni2asc()
The hfsplus_readdir() method is capable to crash by calling hfsplus_uni2asc():
[ 667.121659][ T9805] ==================================================================
[ 667.122651][ T9805] BUG: KASAN: slab-out-of-bounds in hfsplus_uni2asc+0x902/0xa10
[ 667.123627][ T9805] Read of size 2 at addr ffff88802592f40c by task repro/9805
[ 667.124578][ T9805]
[ 667.124876][ T9805] CPU: 3 UID: 0 PID: 9805 Comm: repro Not tainted 6.16.0-rc3 #1 PREEMPT(full)
[ 667.124886][ T9805] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 667.124890][ T9805] Call Trace:
[ 667.124893][ T9805] <TASK>
[ 667.124896][ T9805] dump_stack_lvl+0x10e/0x1f0
[ 667.124911][ T9805] print_report+0xd0/0x660
[ 667.124920][ T9805] ? __virt_addr_valid+0x81/0x610
[ 667.124928][ T9805] ? __phys_addr+0xe8/0x180
[ 667.124934][ T9805] ? hfsplus_uni2asc+0x902/0xa10
[ 667.124942][ T9805] kasan_report+0xc6/0x100
[ 667.124950][ T9805] ? hfsplus_uni2asc+0x902/0xa10
[ 667.124959][ T9805] hfsplus_uni2asc+0x902/0xa10
[ 667.124966][ T9805] ? hfsplus_bnode_read+0x14b/0x360
[ 667.124974][ T9805] hfsplus_readdir+0x845/0xfc0
[ 667.124984][ T9805] ? __pfx_hfsplus_readdir+0x10/0x10
[ 667.124994][ T9805] ? stack_trace_save+0x8e/0xc0
[ 667.125008][ T9805] ? iterate_dir+0x18b/0xb20
[ 667.125015][ T9805] ? trace_lock_acquire+0x85/0xd0
[ 667.125022][ T9805] ? lock_acquire+0x30/0x80
[ 667.125029][ T9805] ? iterate_dir+0x18b/0xb20
[ 667.125037][ T9805] ? down_read_killable+0x1ed/0x4c0
[ 667.125044][ T9805] ? putname+0x154/0x1a0
[ 667.125051][ T9805] ? __pfx_down_read_killable+0x10/0x10
[ 667.125058][ T9805] ? apparmor_file_permission+0x239/0x3e0
[ 667.125069][ T9805] iterate_dir+0x296/0xb20
[ 667.125076][ T9805] __x64_sys_getdents64+0x13c/0x2c0
[ 667.125084][ T9805] ? __pfx___x64_sys_getdents64+0x10/0x10
[ 667.125091][ T9805] ? __x64_sys_openat+0x141/0x200
[ 667.125126][ T9805] ? __pfx_filldir64+0x10/0x10
[ 667.125134][ T9805] ? do_user_addr_fault+0x7fe/0x12f0
[ 667.125143][ T9805] do_syscall_64+0xc9/0x480
[ 667.125151][ T9805] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 667.125158][ T9805] RIP: 0033:0x7fa8753b2fc9
[ 667.125164][ T9805] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 48
[ 667.125172][ T9805] RSP: 002b:00007ffe96f8e0f8 EFLAGS: 00000217 ORIG_RAX: 00000000000000d9
[ 667.125181][ T9805] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa8753b2fc9
[ 667.125185][ T9805] RDX: 0000000000000400 RSI: 00002000000063c0 RDI: 0000000000000004
[ 667.125190][ T9805] RBP: 00007ffe96f8e110 R08: 00007ffe96f8e110 R09: 00007ffe96f8e110
[ 667.125195][ T9805] R10: 0000000000000000 R11: 0000000000000217 R12: 0000556b1e3b4260
[ 667.125199][ T9805] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 667.125207][ T9805] </TASK>
[ 667.125210][ T9805]
[ 667.145632][ T9805] Allocated by task 9805:
[ 667.145991][ T9805] kasan_save_stack+0x20/0x40
[ 667.146352][ T9805] kasan_save_track+0x14/0x30
[ 667.146717][ T9805] __kasan_kmalloc+0xaa/0xb0
[ 667.147065][ T9805] __kmalloc_noprof+0x205/0x550
[ 667.147448][ T9805] hfsplus_find_init+0x95/0x1f0
[ 667.147813][ T9805] hfsplus_readdir+0x220/0xfc0
[ 667.148174][ T9805] iterate_dir+0x296/0xb20
[ 667.148549][ T9805] __x64_sys_getdents64+0x13c/0x2c0
[ 667.148937][ T9805] do_syscall_64+0xc9/0x480
[ 667.149291][ T9805] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 667.149809][ T9805]
[ 667.150030][ T9805] The buggy address belongs to the object at ffff88802592f000
[ 667.150030][ T9805] which belongs to the cache kmalloc-2k of size 2048
[ 667.151282][ T9805] The buggy address is located 0 bytes to the right of
[ 667.151282][ T9805] allocated 1036-byte region [ffff88802592f000, ffff88802592f40c)
[ 667.1
---truncated---
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Analysis
by VulDB Data Team • 02/10/2026
The vulnerability identified as CVE-2025-38713 resides within the Linux kernel's HFS+ filesystem implementation, specifically in the hfsplus_uni2asc() function. This flaw manifests as a slab-out-of-bounds read, a condition that occurs when the kernel attempts to access memory beyond the allocated boundaries of a kernel memory slab. The vulnerability is triggered during directory listing operations through the hfsplus_readdir() method, which internally calls hfsplus_uni2asc() to convert Unicode strings to ASCII. The out-of-bounds read is detected by Kernel Address Sanitizer (KASAN), a memory error detection tool integrated into the Linux kernel. The stack trace confirms that the issue originates from a read operation of size 2 occurring at address ffff88802592f40c, which lies just beyond the allocated 1036-byte region of a kmalloc-2k slab. This type of memory corruption can lead to system instability, data corruption, or potentially exploitable conditions depending on the memory layout and access patterns. The vulnerability is categorized under CWE-125, which describes out-of-bounds read conditions, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter, as malicious actors could potentially leverage such memory corruption to execute arbitrary code or escalate privileges.
The technical root cause of this vulnerability lies in inadequate bounds checking within the hfsplus_uni2asc() function. When processing Unicode data during directory enumeration, the function fails to validate the length of input data against the allocated buffer boundaries. This allows a maliciously crafted HFS+ filesystem or a specially constructed file system structure to cause the kernel to read beyond the intended memory region. The issue is particularly concerning because it occurs during a routine filesystem operation, meaning normal user activities could trigger the vulnerability. The function's failure to enforce proper input validation creates a path for attackers to potentially inject malformed data into the kernel's memory space, leading to unpredictable behavior. The KASAN report indicates that the memory access violation occurs during a read operation, suggesting that the attacker could manipulate the filesystem metadata to force the kernel into reading invalid memory locations. This flaw represents a classic case of insufficient boundary checking in kernel space, where the lack of proper validation allows an attacker to influence kernel memory access patterns.
The operational impact of CVE-2025-38713 extends beyond simple system crashes, as it presents a potential vector for privilege escalation or denial-of-service attacks. When exploited, this vulnerability can cause the kernel to crash or behave unpredictably, leading to system instability and potential data loss. In environments where HFS+ filesystems are in use, particularly in embedded systems or virtualized environments running Linux kernels, this vulnerability could be leveraged to cause system-wide disruptions. The fact that the vulnerability is triggered during directory enumeration operations means that any process attempting to list directory contents on an HFS+ filesystem could potentially trigger the exploit. This makes the vulnerability particularly dangerous in multi-user environments or systems where automated processes routinely access filesystems. The vulnerability's exploitation potential aligns with ATT&CK technique T1499.004 for network denial of service, as system crashes can effectively deny service to legitimate users. Additionally, the memory corruption nature of the flaw could enable more sophisticated attacks if combined with other vulnerabilities or if the attacker can control the memory layout.
Mitigation strategies for CVE-2025-38713 should begin with applying the relevant kernel patch that addresses the slab-out-of-bounds read in hfsplus_uni2asc(). Kernel maintainers have already resolved this issue in the mainline kernel, and organizations should prioritize upgrading to a patched kernel version. In environments where immediate patching is not feasible, administrators can disable HFS+ filesystem support if the filesystem is not actively used, thereby eliminating the attack surface. System administrators should also implement monitoring for unusual system behavior or kernel oops messages that might indicate exploitation attempts. The vulnerability's detection through KASAN provides a clear indicator for security teams to investigate potential exploitation attempts. Regular vulnerability assessments should include checks for outdated kernel versions that might be susceptible to this flaw. Organizations should also consider implementing kernel lockdown mechanisms or other security modules that can restrict kernel memory access patterns. For environments where HFS+ filesystems are essential, deploying additional filesystem validation mechanisms or monitoring tools can help detect malformed filesystem structures before they trigger the vulnerability. The fix implemented by the kernel team typically involves adding proper bounds checking and input validation to ensure that the hfsplus_uni2asc() function does not attempt to read beyond allocated memory boundaries. This aligns with security best practices outlined in the NIST Cybersecurity Framework and ISO/IEC 27001 standards for vulnerability management and system hardening.