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CVE-2025-21632— x86/fpu: Ensure shadow stack is active before "getting" registers

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于在使用影子栈时，未检查影子栈是否已激活，可能导致在访问XSAVE缓冲区时触发警告。

AI Predicted 4.7 Difficulty: Moderate EPSS 0.21% · P11

Possible ATT&CK Techniques 1 AI

T1055 · Process Injection

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9< 0a3a872214188e4268d31581ed0cd44508e038cf affected
2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9< 6bfe1fc22f462bec87422cdcbec4d7a2f43ff01d affected
2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9< a9d9c33132d49329ada647e4514d210d15e31d81 affected
6.6 affected
< 6.6 unaffected
6.6.72≤ 6.6.* unaffected
6.12.10≤ 6.12.* unaffected
6.13≤ * unaffected
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I. Basic Information for CVE-2025-21632

Vulnerability Information
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Vulnerability Title
x86/fpu: Ensure shadow stack is active before "getting" registers
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: x86/fpu: Ensure shadow stack is active before "getting" registers The x86 shadow stack support has its own set of registers. Those registers are XSAVE-managed, but they are "supervisor state components" which means that userspace can not touch them with XSAVE/XRSTOR. It also means that they are not accessible from the existing ptrace ABI for XSAVE state. Thus, there is a new ptrace get/set interface for it. The regset code that ptrace uses provides an ->active() handler in addition to the get/set ones. For shadow stack this ->active() handler verifies that shadow stack is enabled via the ARCH_SHSTK_SHSTK bit in the thread struct. The ->active() handler is checked from some call sites of the regset get/set handlers, but not the ptrace ones. This was not understood when shadow stack support was put in place. As a result, both the set/get handlers can be called with XFEATURE_CET_USER in its init state, which would cause get_xsave_addr() to return NULL and trigger a WARN_ON(). The ssp_set() handler luckily has an ssp_active() check to avoid surprising the kernel with shadow stack behavior when the kernel is not ready for it (ARCH_SHSTK_SHSTK==0). That check just happened to avoid the warning. But the ->get() side wasn't so lucky. It can be called with shadow stacks disabled, triggering the warning in practice, as reported by Christina Schimpe: WARNING: CPU: 5 PID: 1773 at arch/x86/kernel/fpu/regset.c:198 ssp_get+0x89/0xa0 [...] Call Trace: <TASK> ? show_regs+0x6e/0x80 ? ssp_get+0x89/0xa0 ? __warn+0x91/0x150 ? ssp_get+0x89/0xa0 ? report_bug+0x19d/0x1b0 ? handle_bug+0x46/0x80 ? exc_invalid_op+0x1d/0x80 ? asm_exc_invalid_op+0x1f/0x30 ? __pfx_ssp_get+0x10/0x10 ? ssp_get+0x89/0xa0 ? ssp_get+0x52/0xa0 __regset_get+0xad/0xf0 copy_regset_to_user+0x52/0xc0 ptrace_regset+0x119/0x140 ptrace_request+0x13c/0x850 ? wait_task_inactive+0x142/0x1d0 ? do_syscall_64+0x6d/0x90 arch_ptrace+0x102/0x300 [...] Ensure that shadow stacks are active in a thread before looking them up in the XSAVE buffer. Since ARCH_SHSTK_SHSTK and user_ssp[SHSTK_EN] are set at the same time, the active check ensures that there will be something to find in the XSAVE buffer. [ dhansen: changelog/subject tweaks ]
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于在使用影子栈时，未检查影子栈是否已激活，可能导致在访问XSAVE缓冲区时触发警告。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 2fab02b25ae7cf5f714ab456b03d9a3fe5ae98c9 ~ 0a3a872214188e4268d31581ed0cd44508e038cf -
Linux Linux 6.6 -

II. Public POCs for CVE-2025-21632

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III. Intelligence Information for CVE-2025-21632

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Patches & Fixes for CVE-2025-21632 (3)

Same Patch Batch · Linux · 2025-01-19 · 47 CVEs total

CVE-2024-57929 7.8 HIGH dm array: fix releasing a faulty array block twice in dm_array_cursor_end
CVE-2025-21631 7.8 HIGH block, bfq: fix waker_bfqq UAF after bfq_split_bfqq()
CVE-2025-21652 7.8 HIGH ipvlan: Fix use-after-free in ipvlan_get_iflink().
CVE-2024-57918 7.8 HIGH drm/amd/display: fix page fault due to max surface definition mismatch
CVE-2024-57921 7.8 HIGH drm/amdgpu: Add a lock when accessing the buddy trim function
CVE-2024-57926 7.8 HIGH drm/mediatek: Set private->all_drm_private[i]->drm to NULL if mtk_drm_bind returns err
CVE-2025-21646 7.5 HIGH afs: Fix the maximum cell name length
CVE-2025-21647 7.3 HIGH sched: sch_cake: add bounds checks to host bulk flow fairness counts
CVE-2025-21637 7.1 HIGH sctp: sysctl: udp_port: avoid using current->nsproxy
CVE-2025-21650 7.1 HIGH net: hns3: fixed hclge_fetch_pf_reg accesses bar space out of bounds issue
CVE-2025-21640 7.1 HIGH sctp: sysctl: cookie_hmac_alg: avoid using current->nsproxy
CVE-2025-21638 7.1 HIGH sctp: sysctl: auth_enable: avoid using current->nsproxy
CVE-2024-57927 nfs: Fix oops in nfs_netfs_init_request() when copying to cache
CVE-2024-57925 ksmbd: fix a missing return value check bug
CVE-2024-57914 usb: typec: tcpci: fix NULL pointer issue on shared irq case
CVE-2024-57913 usb: gadget: f_fs: Remove WARN_ON in functionfs_bind
CVE-2024-57911 iio: dummy: iio_simply_dummy_buffer: fix information leak in triggered buffer
CVE-2024-57910 iio: light: vcnl4035: fix information leak in triggered buffer
CVE-2024-57916 misc: microchip: pci1xxxx: Resolve kernel panic during GPIO IRQ handling
CVE-2024-57912 iio: pressure: zpa2326: fix information leak in triggered buffer

Showing top 20 of 47 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21632

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