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CVE-2026-89634— smb: client: fix ALIGN() overflow in symlink_data() error context loop

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基金会开源的一个操作系统内核。 Linux kernel 6.1版本存在安全漏洞，该漏洞源于smb client中symlink_data()错误上下文循环对ALIGN()的检查不当，ErrorDataLength接近UINT32_MAX时ALIGN()运算溢出，导致边界检查通过并使循环零字节推进，可能造成越界读取和无限循环。

CVSS 9.1 · Critical EPSS 0.70% · P52

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 76894f3e2f71177747b8b4763fb180e800279585< 2b4a25baa0b936fef6915c0459925077b324ecaf affected
76894f3e2f71177747b8b4763fb180e800279585< b89d678f9eafcf8d74885983166ba26b40a04ea0 affected
76894f3e2f71177747b8b4763fb180e800279585< 657372ba6ea50b4474d2a6a610097eae8cd1f3e9 affected
76894f3e2f71177747b8b4763fb180e800279585< 1f824f61d1df52392eaf0b74dfa5659d724fde30 affected
76894f3e2f71177747b8b4763fb180e800279585< 62a3025983c8c735a3c6fc85a59316f31b59af07 affected
76894f3e2f71177747b8b4763fb180e800279585< 62656b024efc21c3230eade1a847f25871c3d2bb affected
2d046892a493d9760c35fdaefc3017f27f91b621 affected
6.0.16< 6.1 affected
… +8 more rows
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I. Basic Information for CVE-2026-89634

Vulnerability Information
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Vulnerability Title
smb: client: fix ALIGN() overflow in symlink_data() error context loop
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix ALIGN() overflow in symlink_data() error context loop The check added by commit 7d9a7f1f96cd ("smb/client: fix possible infinite loop and oob read in symlink_data()") compared the post-ALIGN length against the remaining buffer, but ALIGN() itself can overflow: for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8) wraps to 0, so the subsequent bounds check passes, and the loop advances by zero bytes leaving 'p' pointing into stale data. Fix by checking the raw ErrorDataLength against the remaining space before applying ALIGN(), then checking again after. Since raw_len is bounded by the buffer, raw_len + 7 cannot overflow, so the second check is an exact post-alignment bounds guard.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/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基金会开源的一个操作系统内核。 Linux kernel 6.1版本存在安全漏洞，该漏洞源于smb client中symlink_data()错误上下文循环对ALIGN()的检查不当，ErrorDataLength接近UINT32_MAX时ALIGN()运算溢出，导致边界检查通过并使循环零字节推进，可能造成越界读取和无限循环。
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 76894f3e2f71177747b8b4763fb180e800279585 ~ 2b4a25baa0b936fef6915c0459925077b324ecaf -
Linux Linux 6.1 -

II. Public POCs for CVE-2026-89634

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III. Intelligence Information for CVE-2026-89634

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Patches & Fixes for CVE-2026-89634 (6)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89656 9.8 CRITICAL libceph: reject buckets with mismatched CRUSH ids
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown

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

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-89634

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