System crash via oversized OCFS2 bitmap descriptor
Published Jul 19, 2026 · Updated Jul 19, 2026
Out-of-bounds access in OCFS2 in Linux Kernel allows remote authenticated users to crash a server through a malicious group descriptor. ocfs2_validate_gd_parent() accepts bg_size and bg_bits values larger than the bitmap bytes in the descriptor block, so later scans and updates pass bg_bitmap. Exploitation requires attacker-planted metadata on a mounted OCFS2 volume and write access that reaches cluster allocation; the reproduced consequence is a kernel fault and service interruption.
Summary
What happened
Out-of-bounds access in OCFS2 in Linux Kernel allows remote authenticated users to crash a server through a malicious group descriptor. ocfs2_validate_gd_parent() accepts bg_size and bg_bits values larger than the bitmap bytes in the descriptor block, so later scans and updates pass bg_bitmap. Exploitation requires attacker-planted metadata on a mounted OCFS2 volume and write access that reaches cluster allocation; the reproduced consequence is a kernel fault and service interruption.
The record
- CVE
- CVE-2026-63796
- Published
- Jul 19, 2026
- Updated
- Jul 19, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux Kernel
- Classifications
- T1210
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 19, 2026CVE publishedPublication date reported by the CVE source.
- Jul 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
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- Affected versionversion=2.6.16
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <296c6a42b1174395935ca4cfe8f393e37b698d54
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <336340a0f8a141df8a4eb21a5a86f8ffb87769f6
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <4cd57ebee395041099fcdfcabb00749ce38d8b27
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <8f9903b0cdbb3155a8899410330b4b4d583a7a5c
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <99c21e7263248c3f084756bfae08163cc5d6c62f
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <9bd541e09dffff27e5bec0f9f45b0228173a5375
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <c5a125eadba05ba421c4b55e68da22b4a40d32b4
- Affected versionversion=ccd979bdbce9fba8412beb3f1de68a9d0171b12c <d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e
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Attacks
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