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CVE-2026-97559— smb: client: fail DACL rewrite when the new DACL exceeds 64K

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.

在 Linux 内核中，已修复以下漏洞： smb：客户端：当新 DACL 超过 64KB 时，拒绝重写 DACL 和 函数使用一个 （16 位无符号整数）来累计所构建 DACL（离散访问控制列表）的大小。该累加器可能发生溢出（wrap around）。 函数将 限制为 ，即对于最大尺寸的 DACL，最多允许 3276 个 ACE（访问控制条目）。然而，每个被重写的 ACE 在将其 SID（安全标识符）替换为携带 个子授权数的 SID 后，其大小可扩展至 （76 字节）。因此，最坏情况下的总大小为： 字节，远远超出

AI Predicted 6.5 Difficulty: Moderate EPSS 0.20% · P9

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 10

VendorProduct Version RangeStatus
Linux Linux f5065508897a922327f32223082325d10b069ebc< d433376abc47e10870ae732f89c7c1a60b199a0c affected
f5065508897a922327f32223082325d10b069ebc< 2ef532a01f44687f5b95001e88247cf05bff9892 affected
f5065508897a922327f32223082325d10b069ebc< ee13d687d06a6fbb2008625dd560c654231b28e0 affected
f5065508897a922327f32223082325d10b069ebc< d05045177a855386bca5e1909e08d06290e6e3b3 affected
5.12 affected
< 5.12 unaffected
6.12.112≤ 6.12.* unaffected
6.18.53≤ 6.18.* unaffected
… +2 more rows
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I. Basic Information for CVE-2026-97559

Vulnerability Information
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Vulnerability Title
smb: client: fail DACL rewrite when the new DACL exceeds 64K
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: fail DACL rewrite when the new DACL exceeds 64K replace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of the DACL they build in a u16. That accumulator can wrap. validate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) / 20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can grow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with one carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is therefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond what a u16 can hold. A wraparound is reached with 863 ACEs. After the wraparound, ndacl_ptr->size becomes meaningless and the offset will point anywhere in the ACE array. As a result, we will see corruption of the DACL, which then gets sent to the server. This is not an out-of-bounds write as the allocation now covers the worst-case expansion, so writes will always go into the buffer. Adjust the code to use a u32 internally and return -EOVERFLOW in the overflow case. The operation must be refused, because a DACL can only hold 2^16-1 bytes on the wire and larger DACLs cannot be represented. set_chmod_dacl() carries the same pattern and is fixed the same way. It only wraps once the source DACL comes within roughly 380 bytes of the 64K ceiling, but the failure mode is identical.
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

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux f5065508897a922327f32223082325d10b069ebc ~ d433376abc47e10870ae732f89c7c1a60b199a0c -
Linux Linux 5.12 -

II. Public POCs for CVE-2026-97559

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III. Intelligence Information for CVE-2026-97559

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Patches & Fixes for CVE-2026-97559 (4)

Same Patch Batch · Linux · 2026-09-25 · 372 CVEs total

CVE-2026-100075 9.8 CRITICAL RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters
CVE-2026-97957 8.8 HIGH net: hinic: fix mailbox segment buffer overflow
CVE-2026-97527 8.8 HIGH scsi: qla2xxx: Serialize NVMe unsol ctx list with a per-fcport lock
CVE-2026-97528 8.8 HIGH scsi: qla2xxx: Unlink NVMe unsol ctx before freeing on LS reject error
CVE-2026-97555 8.8 HIGH smb: client: fix heap overflow in DACL owner/group rewrite
CVE-2026-98115 8.8 HIGH ksmbd: safely drain sessions during logoff
CVE-2026-97525 8.2 HIGH x86/mm/pat: Allocate split page tables as kernel page tables
CVE-2026-97573 8.1 HIGH bnxt_en: Handle buffer allocation failure in bnxt_rx_ring_reset()
CVE-2026-98070 8.1 HIGH net/rds: acquire RDS_IN_XMIT in rds_tcp_reset_callbacks()
CVE-2026-97570 8.1 HIGH bnxt_en: Bound SW TPA IDs to prevent crashes
CVE-2026-98069 8.1 HIGH net/rds: acquire the fastpath locks in rds_conn_shutdown()
CVE-2026-98130 8.1 HIGH sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START
CVE-2026-98116 7.8 HIGH ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF
CVE-2026-97903 7.8 HIGH exit: hold a reference to thread_pid across proc_flush_pid
CVE-2026-97548 7.8 HIGH xfs: fix the rtrmap and rtrefcount _maxlevels_ondisk functions
CVE-2026-97611 7.8 HIGH net: openvswitch: fix use-after-free of the flow table mask array
CVE-2026-97612 7.8 HIGH net: mpls: clear inner_protocol when the last label is popped
CVE-2026-98073 7.8 HIGH net: Remove conflicting altnames for dying netns in __dev_change_net_namespace().
CVE-2026-97602 7.8 HIGH inet: frags: invalidate queues before flushing them
CVE-2026-97577 7.8 HIGH media: verisilicon: rockchip: reject AV1 frames exceeding the tile capacity

Showing top 20 of 372 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-97559

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