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CVE Record

CVE-2025-40049: Squashfs: fix uninit-value in squashfs_get_parent

In the Linux kernel, the following vulnerability has been resolved: Squashfs: fix uninit-value in squashfs_get_parent Syzkaller reports a "KMSAN: uninit-value in squashfs_get_parent" bug. This is caused by open_by_handle_at() being called with a file handle containing an invalid parent inode number. In particular the inode number is that of a symbolic link, rather than a directory. Squashfs_get_parent() gets called with that symbolic link inode, and accesses the parent member field. unsigned int parent_ino = squashfs_i(inode)->parent; Because non-directory inodes in Squashfs do not have a parent value, this is uninitialised, and this causes an uninitialised value access. The fix is to initialise parent with the invalid inode 0, which will cause an EINVAL error to be returned. Regular inodes used to share the parent field with the block_list_start field. This is removed in this commit to enable the parent field to contain the invalid inode number 0.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue is in Squashfs handling. A crafted invalid file handle can make the kernel read an uninitialized parent field for a non-directory inode. The provided sources describe the bug and code fix, but do not state business impact, CVSS severity, or active exploitation.

Executive priority

Track this as a kernel hygiene update, not an emergency, unless your environment processes untrusted Squashfs images. No active exploitation or severity score is provided, so prioritize through normal Linux patch governance with attention to exposed Squashfs workflows.

Technical view

squashfs_get_parent() can be reached through open_by_handle_at() with a file handle whose parent inode number points to a symbolic link, not a directory. Squashfs non-directory inodes lack a valid parent value, causing an uninitialized value access. The kernel fix initializes parent to inode 0 so EINVAL is returned.

Likely exposure

Exposure is limited to Linux systems running affected kernel versions with Squashfs code reachable. The bundle lists Linux kernel versions including 2.6.29 and stable branch points through 6.18, but precise distribution package impact is not provided.

Exploitation context

The source bundle does not cite public exploitation, weaponized proof of concept, or CISA KEV listing. The issue was reported by Syzkaller/KMSAN, suggesting automated kernel testing found it. Treat exploitability and real-world impact as unproven from these sources.

Researcher notes

Key evidence is the kernel description: invalid parent inode via open_by_handle_at(), symlink inode passed to squashfs_get_parent(), uninitialized parent field read, and fix by initializing parent to invalid inode 0. Impact classification, privilege requirements, and exploitability are not established in the bundle.

Mitigation direction

  • Check your Linux vendor advisory for fixed kernel packages for CVE-2025-40049.
  • Prioritize updates on systems that mount or process Squashfs filesystems.
  • Deploy kernel versions containing the referenced upstream stable commits when vendor-approved.
  • If patching is delayed, restrict untrusted Squashfs handling where operationally possible.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and images.
  • Check whether deployed kernels include one of the referenced stable fix commits.
  • Review vendor kernel changelogs for CVE-2025-40049 or the Squashfs parent initialization fix.
  • Confirm whether systems mount or ingest Squashfs content from untrusted sources.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
9Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2, 122601408d20c77704268f1dea9f9ce4abf997c2unaffected
LinuxLinux2.6.29, 0, 5.4.301, 5.10.246, 5.15.195, 6.1.156, 6.6.112, 6.12.53, 6.17.3, 6.18affected
Weakness

CWE details

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