btrfs: avoid potential out-of-bounds in btrfs_encode_fh()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-40205
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-11-12 22:15:47 UTC
Updated2026-07-30 06:24:17 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: btrfs: avoid potential out-of-bounds in btrfs_encode_fh() The function btrfs_encode_fh() does not properly account for the three cases it handles. Before writing to the file handle (fh), the function only returns to the user BTRFS_FID_SIZE_NON_CONNECTABLE (5 dwords, 20 bytes) or BTRFS_FID_SIZE_CONNECTABLE (8 dwords, 32 bytes). However, when a parent exists and the root ID of the parent and the inode are different, the function writes BTRFS_FID_SIZE_CONNECTABLE_ROOT (10 dwords, 40 bytes). If *max_len is not large enough, this write goes out of bounds because BTRFS_FID_SIZE_CONNECTABLE_ROOT is greater than BTRFS_FID_SIZE_CONNECTABLE originally returned. This results in an 8-byte out-of-bounds write at fid->parent_root_objectid = parent_root_id. A previous attempt to fix this issue was made but was lost. https://lore.kernel.org/all/[email protected]/ Although this issue does not seem to be easily triggerable, it is a potential memory corruption bug that should be fixed. This patch resolves the issue by ensuring the function returns the appropriate size for all three cases and validates that *max_len is large enough before writing any data.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001410000 probability, percentile 0.039050000 (date 2026-07-31)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 60de2f55d2aca53e81b4ef2a67d7cc9e1eb677db git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 742b44342204e5dfe3926433823623c1a0c581df git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 d3a9a8e1275eb9b87f006b5562a287aea3f6885f git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 d91f6626133698362bba08fbc04bd72c466806d3 git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 0276c8582488022f057b4cec21975a5edf079f47 git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 361d67276eb8ec6be8f27f4ad6c6090459438fee git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 43143776b0a7604d873d1a6f3e552a00aa930224 git Not specified
CNA Linux Linux affected be6e8dc0ba84029997075a1ec77b4ddb863cbe15 dff4f9ff5d7f289e4545cc936362e01ed3252742 git Not specified
CNA Linux Linux affected 2.6.29 Not specified
CNA Linux Linux unaffected 2.6.29 semver Not specified
CNA Linux Linux unaffected 5.4.301 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.246 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.195 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.157 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.113 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.54 6.12.* semver Not specified
CNA Linux Linux unaffected 6.17.4 6.17.* semver Not specified
CNA Linux Linux unaffected 6.18 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/742b44342204e5dfe3926433823623c1a0c581df 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0276c8582488022f057b4cec21975a5edf079f47 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/60de2f55d2aca53e81b4ef2a67d7cc9e1eb677db 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dff4f9ff5d7f289e4545cc936362e01ed3252742 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/361d67276eb8ec6be8f27f4ad6c6090459438fee 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d91f6626133698362bba08fbc04bd72c466806d3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/43143776b0a7604d873d1a6f3e552a00aa930224 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d3a9a8e1275eb9b87f006b5562a287aea3f6885f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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