Bug 2535078 (CVE-2026-89782)

Summary: CVE-2026-89782 kernel: fs/ntfs3: reject restart table growth beyond U16_MAX entries
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
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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A flaw was found in the Linux kernel's NTFS3 file system driver. A local attacker can exploit this vulnerability by mounting a specially crafted NTFS image. During the processing of the $LogFile, an integer truncation error occurs when attempting to grow the restart table, leading to an out-of-bounds write. This can result in a denial of service or potentially lead to arbitrary code execution.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-09-16 09:13:12 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: reject restart table growth beyond U16_MAX entries

During $LogFile replay, log_replay() indexes the transaction table by the
transact_id taken from the log record header.  check_log_rec() only
verifies that transact_id is non-zero and properly aligned, not its
magnitude, so a crafted image can request an arbitrarily large index.

alloc_rsttbl_from_idx() grows the table to cover that index via
extend_rsttbl(), which passes the new entry count to init_rsttbl():

	rt = init_rsttbl(esize, used + add);

used + add is computed as u32 but init_rsttbl() takes a u16, and the
count is stored in struct RESTART_TABLE as a __le16.  When used + add
exceeds U16_MAX it is truncated, init_rsttbl() allocates a table far
smaller than the index requires, and alloc_rsttbl_from_idx() then
dereferences and writes at the original, untruncated offset -- an
out-of-bounds access past the allocation, reachable by mounting a
crafted NTFS image.

 BUG: KASAN: use-after-free in alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950)
 Read of size 4 at addr ffff8880327ffff8 by task exploit
  alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950)
  log_replay (fs/ntfs3/fslog.c:4562)
  ntfs_loadlog_and_replay (fs/ntfs3/fsntfs.c:324)
  ntfs_fill_super (fs/ntfs3/super.c:1393)
  get_tree_bdev_flags
  vfs_get_tree
  path_mount
  __x64_sys_mount

A restart table is limited to U16_MAX entries by its __le16 count, so a
larger growth request is invalid input.  Reject it in extend_rsttbl();
all callers already handle a NULL return.
Comment 1 Keith Grant 2026-09-21 19:39:17 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89782.mbox