Bug 2546374 (CVE-2026-98318)

Summary: CVE-2026-98318 kernel: smb: client: validate absolute native symlink targets before NT fixups
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's SMB (Server Message Block) client. When handling absolute symbolic links on mounted shares, the client fails to validate the link target format before applying Windows NT path adjustments. A user with write access to a mounted share can exploit this vulnerability by creating a specially crafted symbolic link, triggering out-of-bounds memory writes and a buffer overflow. This flaw can result in a Denial of Service (DoS) by crashing the system or potentially allow arbitrary code execution.
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Description OSIDB Bzimport 2026-10-06 09:08:14 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: validate absolute native symlink targets before NT fixups

With symlinkroot unset, an absolute target is copied without conversion
to an NT drive path. Later code still assumes an NT prefix is present
when modifying the target and calculating the print name length.

For "/ab", this causes two failures: sym[5] and path[5] are written
past their allocations, and plen -= 2 * poff subtracts an assumed
8-byte prefix from a 6-byte UTF-16 target, wrapping u16 plen to 65534.
That underflow causes another overflow: memcpy() copies 65534 bytes
into a 24-byte buffer. A user with write access to a mounted share
can trigger these bugs with default settings.

Validate the NT drive prefix, including an ASCII drive letter, before
accessing fixed offsets or subtracting the prefix length.
Comment 1 gkamathe 2026-10-10 03:33:05 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98318.mbox