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CVE-2026-63952— memfd: deny writeable mappings when implying SEAL_WRITE

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 6.3版本存在安全漏洞，该漏洞源于memfd中的密封检查顺序问题，当添加SEAL_EXEC时，隐含的SEAL_WRITE会在可写映射检查之后设置，攻击者可能利用此漏洞传递看似已写密封但仍可任意修改的memfd。

CVSS 8.4 · High EPSS 0.16% · P6

Possible ATT&CK Techniques 1 AI

T1564.004 · NTFS File Attributes

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux c4f75bc8bd6b3d62665e1f5400c419540edb5601< b3f4f82d1315f1439059a83d1c22c51a5b43d99e affected
c4f75bc8bd6b3d62665e1f5400c419540edb5601< 3be2a24f7f72ad7321ed6ad1715b956a4527bcf4 affected
c4f75bc8bd6b3d62665e1f5400c419540edb5601< 0995d1f79aed8ccbf62056189dd53fd19726ea08 affected
c4f75bc8bd6b3d62665e1f5400c419540edb5601< 555702282d4536a865dfffb1cd4f6028f196e7e8 affected
c4f75bc8bd6b3d62665e1f5400c419540edb5601< 3b041514cb6eae45869b020f743c14d983363222 affected
6.3 affected
< 6.3 unaffected
6.6.143≤ 6.6.* unaffected
… +4 more rows
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I. Basic Information for CVE-2026-63952

Vulnerability Information
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Vulnerability Title
memfd: deny writeable mappings when implying SEAL_WRITE
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: memfd: deny writeable mappings when implying SEAL_WRITE When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings. This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily. Fix this by adding the implied seals before the call for mapping_deny_writable() is done.
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:N
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 6.3版本存在安全漏洞，该漏洞源于memfd中的密封检查顺序问题，当添加SEAL_EXEC时，隐含的SEAL_WRITE会在可写映射检查之后设置，攻击者可能利用此漏洞传递看似已写密封但仍可任意修改的memfd。
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 c4f75bc8bd6b3d62665e1f5400c419540edb5601 ~ b3f4f82d1315f1439059a83d1c22c51a5b43d99e -
Linux Linux 6.3 -

II. Public POCs for CVE-2026-63952

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III. Intelligence Information for CVE-2026-63952

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Patches & Fixes for CVE-2026-63952 (5)

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-2026-64037 9.8 CRITICAL wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
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-2026-63886 9.8 CRITICAL scsi: target: iscsi: Validate CHAP_R length before base64 decode
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-64122 9.8 CRITICAL net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover
CVE-2026-64150 9.8 CRITICAL netfilter: nft_inner: release local_lock before re-enabling softirqs
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
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-2026-64007 9.8 CRITICAL netfilter: synproxy: refresh tcphdr after skb_ensure_writable
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-2026-63952

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