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CVE-2026-63941— KVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor

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基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于ZCR_EL2寄存器处理不当，可能导致L2客户机访问不应有的向量长度。以下版本受到影响：6.11版本。

CVSS 8.8 · High EPSS 0.17% · P6

Possible ATT&CK Techniques 1 AI

T1498 · Network Denial of Service

Affected Version Matrix 6

VendorProduct Version RangeStatus
Linux Linux b3d29a8230998b36afecf494b199211d26052785< 742a9b5ccd8c46caf983ca90c94f855466968e34 affected
b3d29a8230998b36afecf494b199211d26052785< 83726330748981372bde86ed5411d7b306612991 affected
6.11 affected
< 6.11 unaffected
7.0.12≤ 7.0.* unaffected
7.1≤ * unaffected
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I. Basic Information for CVE-2026-63941

Vulnerability Information
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Vulnerability Title
KVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor ZCR_EL2 can be updated by a VHE guest hypervisor either using ZCR_EL2 (which traps) or ZCR_EL1 (which does not trap). KVM handles both in different way: - on ZCR_EL2 trap, ZCR_EL2.LEN is immediately capped at the VM's own VL limit. This has the potential to break existing SW that relies on the full LEN field to be stateful. - on ZCR_EL1 access, we do absolutely nothing. On restoring the SVE context for an L2 guest, we directly restore the guest hypervisor's view of ZCR_EL2 into the physical ZCR_EL2. If the guest's view of the register was updated using the ZCR_EL2 accessor, the value has already been sanitised (with the caveat mentioned above). But if the guest used ZCR_EL1, the raw value is written into the HW, and the L2 guest can now access VLs that it shouldn't. Fix all the above by moving the VL capping to the restore points, ensuring that: - the HW is always programmed with a capped value, irrespective of the accessor being used, - the ZCR_EL2.LEN field is always completely stateful, irrespective of the accessor being used. Additionally, move ZCR_EL2 to be a sanitised register, ensuring that only the LEN field is actually stateful. This requires some creative construction of the RES0 mask, as the sysreg generation script does not yet generate RAZ/WI fields. [maz: rewrote commit message, tidy up access_zcr_el2()]
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
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基金会开源的一款操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于ZCR_EL2寄存器处理不当，可能导致L2客户机访问不应有的向量长度。以下版本受到影响：6.11版本。
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 b3d29a8230998b36afecf494b199211d26052785 ~ 742a9b5ccd8c46caf983ca90c94f855466968e34 -
Linux Linux 6.11 -

II. Public POCs for CVE-2026-63941

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III. Intelligence Information for CVE-2026-63941

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Patches & Fixes for CVE-2026-63941 (2)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-64089 9.8 CRITICAL batman-adv: tt: fix negative last_changeset_len
CVE-2026-53398 9.8 CRITICAL NFSD: Fix SECINFO_NO_NAME decode error cleanup
CVE-2026-64142 9.8 CRITICAL ksmbd: close durable scavenger races against m_fp_list lookups
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-64037 9.8 CRITICAL wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-63886 9.8 CRITICAL scsi: target: iscsi: Validate CHAP_R length before base64 decode
CVE-2026-64035 9.8 CRITICAL igc: set tx buffer type for SMD frames
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-64122 9.8 CRITICAL net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-64150 9.8 CRITICAL netfilter: nft_inner: release local_lock before re-enabling softirqs
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-64025 9.8 CRITICAL bpf, skmsg: fix verdict sk_data_ready racing with ktls rx
CVE-2026-64102 9.8 CRITICAL RDMA/siw: Reject MPA FPDU length underflow before signed receive math
CVE-2026-63993 9.8 CRITICAL vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
CVE-2026-63994 9.8 CRITICAL tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-63941

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