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CVE-2026-63909— ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops

CVSS 8.1 · High EPSS 0.63% · P46

Possible ATT&CK Techniques 1AI

T1059 · Command and Scripting Interpreter

Affected Version Matrix 11

VendorProductVersion RangeStatus
LinuxLinux282cbbb476b9f35793452bc461934af4c7eca169< 5500ba1d410aed1eded3eb04a76b10cfb4409334affected
f20adc4ef7428bc485ee83fd1a592252fb87718b< f6324b4240cf0b26a84c33f68a1222d727ff4af2affected
325d4ac11f526cb8964cff14548ccf02d8c756d8< 0fe08c5776a798f46df1fd74b331be26bdd644d6affected
95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c< d333af32e4451285e427f2d9c29de3a39f6f6d48affected
90089584b2e25c4510b7b987387b4405f0673ece< 94215d55b09445993929f4fc966061d61de74929affected
151b1799861fde38087c08f613abc2843ef597b0< 4f7c131d2bdd7cd64b96f60d10be5ea72253f520affected
d07b26f39246a82399661936dd0c853983cfade7< 0e60dafe97eca61721f3db456f97d97a80c6c8aeaffected
6.6.140< 6.6.143affected
… +3 more rows
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I. Basic Information for CVE-2026-63909

Vulnerability Information
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Vulnerability Title
ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops Commit d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()") introduced a transposed bounds check: if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE) Since offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates to `aces_size < 0`. Because `aces_size` is always non-negative, this check becomes dead code and never breaks the loop. Worse, that commit removed the old 4-byte guard, meaning the loop now reads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This re-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation during subsequent SMB2_CREATE operations. Fix this by properly transposing the comparison to require at least 16 bytes (8-byte offset + 8-byte SID base), matching the correct form used in smb_inherit_dacl().
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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smb_check_perm_dacl()函数中的边界检查错误，导致越界读取。
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

VendorProductAffected VersionsCPESubscribe
LinuxLinux 282cbbb476b9f35793452bc461934af4c7eca169 ~ 5500ba1d410aed1eded3eb04a76b10cfb4409334 -
LinuxLinux 6.6.140 ~ 6.6.143 -

II. Public POCs for CVE-2026-63909

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III. Intelligence Information for CVE-2026-63909

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Patches & Fixes for CVE-2026-63909 (7)

Same Patch Batch · Linux · 2026-07-19 · 431 CVEs total

CVE-2026-6379510.0 CRITICAL9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-639229.8 CRITICALipv6: exthdrs: refresh nh after handling HAO option
CVE-2026-641369.8 CRITICALsmb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()
CVE-2026-641509.8 CRITICALnetfilter: nft_inner: release local_lock before re-enabling softirqs
CVE-2026-639249.8 CRITICALipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo()
CVE-2026-640009.8 CRITICALnet: hsr: fix potential OOB access in supervision frame handling
CVE-2026-640469.8 CRITICALnet: tls: prevent chain-after-chain in plain text SG
CVE-2026-640479.8 CRITICALnet: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring
CVE-2026-639949.8 CRITICALtunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()
CVE-2026-641429.8 CRITICALksmbd: close durable scavenger races against m_fp_list lookups
CVE-2026-639939.8 CRITICALvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()
CVE-2026-533989.8 CRITICALNFSD: Fix SECINFO_NO_NAME decode error cleanup
CVE-2026-641329.8 CRITICALipv6: ioam: refresh hdr pointer before ioam6_event()
CVE-2026-533999.8 CRITICALnfsd: release layout stid on setlease failure
CVE-2026-640559.8 CRITICALnet: ethernet: cortina: Carry over frag counter
CVE-2026-641259.8 CRITICALnet: bcmgenet: keep RBUF EEE/PM disabled
CVE-2026-641229.8 CRITICALnet/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover
CVE-2026-638579.8 CRITICALnet: airoha: Do not read uninitialized fragment address in airoha_dev_xmit()
CVE-2026-639799.8 CRITICALnet/handshake: hand off the pinned file reference to accept_doit
CVE-2026-639789.8 CRITICALnet/handshake: Drain pending requests at net namespace exit

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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