Linux: Out-of-bounds Read
CVE-2026-63796 is a high-severity out-of-bounds read vulnerability in Linux, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists versions 336340a0f8a141df8a4eb21a5a86f8ffb87769f6, 296c6a42b1174395935ca4cfe8f393e37b698d54, d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.59% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 336340a0f8a141df8a4eb21a5a86f8ffb87769f6 or 296c6a42b1174395935ca4cfe8f393e37b698d54 or d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e or c5a125eadba05ba421c4b55e68da22b4a40d32b4, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.260 or 5.15.211 or 6.1.177 or 6.6.144, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, 336340a0f8a141df8a4eb21a5a86f8ffb87769f6; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, 296c6a42b1174395935ca4cfe8f393e37b698d54; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, c5a125eadba05ba421c4b55e68da22b4a40d32b4; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, 8f9903b0cdbb3155a8899410330b4b4d583a7a5c; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, 4cd57ebee395041099fcdfcabb00749ce38d8b27; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, 99c21e7263248c3f084756bfae08163cc5d6c62f; ccd979bdbce9fba8412beb3f1de68a9d0171b12c up to, but not including, 9bd541e09dffff27e5bec0f9f45b0228173a5375; and 1 more ranges | 336340a0f8a141df8a4eb21a5a86f8ffb87769f6, 296c6a42b1174395935ca4cfe8f393e37b698d54, d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e, c5a125eadba05ba421c4b55e68da22b4a40d32b4, 8f9903b0cdbb3155a8899410330b4b4d583a7a5c, 4cd57ebee395041099fcdfcabb00749ce38d8b27 |
| Linux | Linux Kernel | 2.6.16 up to, but not including, 5.10.260; 5.11 up to, but not including, 5.15.211; 5.16 up to, but not including, 6.1.177; 6.2 up to, but not including, 6.6.144; 6.7 up to, but not including, 6.12.95; 6.13 up to, but not including, 6.18.38; 6.19 up to, but not including, 7.1.3 | 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: ocfs2: reject oversized group bitmap descriptors ocfs2_validate_gd_parent() only bounds bg_bits against the parent allocator's chain geometry. A malicious descriptor can still claim a bg_size/bg_bits pair that exceeds the bitmap bytes that physically fit in the group descriptor block, so later bitmap scans and bit updates can run past bg_bitmap. Add a physical-cap check based on ocfs2_group_bitmap_size() for the parent allocator type and reject descriptors whose bg_size or bg_bits exceed that capacity. Keep the existing chain geometry check so both the on-disk bitmap layout and the allocator metadata must agree before the descriptor is used. Validation reproduced this kernel report: KASAN use-after-free in _find_next_bit+0x7f/0xc0 Read of size 8 Call trace: dump_stack_lvl+0x66/0xa0 (?:?) print_report+0xd0/0x630 (?:?) _find_next_bit+0x7f/0xc0 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) __virt_addr_valid+0x188/0x2f0 (?:?) kasan_report+0xe4/0x120 (?:?) ocfs2_find_max_contig_free_bits+0x35/0x70 (fs/ocfs2/suballoc.c:1375) ocfs2_block_group_set_bits+0x472/0x4b0 (fs/ocfs2/suballoc.c:1457) ocfs2_cluster_group_search+0x16b/0x440 (fs/ocfs2/suballoc.c:86) ocfs2_bg_discontig_fix_result+0x1ef/0x230 (fs/ocfs2/suballoc.c:1786) ocfs2_search_chain+0x8f8/0x10a0 (fs/ocfs2/suballoc.c:1886) get_page_from_freelist+0x70e/0x2370 (?:?) lock_release+0xc6/0x290 (?:?) do_raw_spin_unlock+0x9a/0x100 (?:?) kasan_unpoison+0x27/0x60 (?:?) __bfs+0x147/0x240 (?:?) get_page_from_freelist+0x83d/0x2370 (?:?) ocfs2_claim_suballoc_bits+0x38c/0xe70 (fs/ocfs2/suballoc.c:96) sched_domains_numa_masks_clear+0x70/0xd0 (?:?) check_irq_usage+0xe8/0xb70 (?:?) __ocfs2_claim_clusters+0x18d/0x4c0 (fs/ocfs2/suballoc.c:2497) check_path+0x24/0x50 (?:?) rcu_is_watching+0x20/0x50 (?:?) check_prev_add+0xfd/0xd00 (?:?) ocfs2_add_clusters_in_btree+0x17d/0x810 (fs/ocfs2/suballoc.c:?) __folio_batch_add_and_move+0x1f5/0x3d0 (?:?) ocfs2_add_inode_data+0xd9/0x120 (fs/ocfs2/suballoc.c:?) filemap_add_folio+0x105/0x1f0 (?:?) ocfs2_write_begin_nolock+0x29f7/0x2f80 (fs/ocfs2/suballoc.c:3043) ocfs2_read_inode_block+0xb5/0x110 (fs/ocfs2/suballoc.c:?) down_write+0xf5/0x180 (?:?) ocfs2_write_begin+0x180/0x240 (fs/ocfs2/suballoc.c:?) __mark_inode_dirty+0x758/0x9a0 (?:?) inode_to_bdi+0x41/0x90 (?:?) balance_dirty_pages_ratelimited_flags+0xf8/0x1d0 (?:?) generic_perform_write+0x252/0x440 (?:?) mnt_put_write_access_file+0x16/0x70 (?:?) file_update_time_flags+0xe4/0x200 (?:?) ocfs2_file_write_iter+0x80a/0x1320 (fs/ocfs2/suballoc.c:?) lock_acquire+0x184/0x2f0 (?:?) ksys_write+0xd2/0x170 (?:?) apparmor_file_permission+0xf5/0x310 (?:?) read_zero+0x8d/0x140 (?:?) lock_is_held_type+0x8f/0x100 (?:?)
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/296c6a42b1174395935ca4cfe8f393e37b698d54
- git.kernel.org/stable/c/336340a0f8a141df8a4eb21a5a86f8ffb87769f6
- git.kernel.org/stable/c/4cd57ebee395041099fcdfcabb00749ce38d8b27
- git.kernel.org/stable/c/8f9903b0cdbb3155a8899410330b4b4d583a7a5c
- git.kernel.org/stable/c/99c21e7263248c3f084756bfae08163cc5d6c62f
- git.kernel.org/stable/c/9bd541e09dffff27e5bec0f9f45b0228173a5375
- git.kernel.org/stable/c/c5a125eadba05ba421c4b55e68da22b4a40d32b4
- git.kernel.org/stable/c/d2cd59fa848f9f13796ef214d3b1b5ca9a3fe21e
Recent Out-of-bounds Read vulnerabilities
- 7.1 High severity
- 7.8 High severity
- 7.3 High severity
- 7.1 High severity
- 7.8 High severity
- 9.8 Critical severity
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