High 7.8Published Apr 1, 2026

CVE-2026-23406apparmor: fix side-effect bug in match_char() macro usage

Updated under an hour ago (Oct 27, 2026, 12:00 PM ET)

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In the Linux kernel, the following vulnerability has been resolved: apparmor: fix side-effect bug in match_char() macro usage The match_char() macro evaluates its character parameter multiple times when traversing differential encoding chains. When invoked with *str++, the string pointer advances on each iteration of the inner do-while loop, causing the DFA to check different characters at each iteration and therefore skip input characters. This results in out-of-bounds reads when the pointer advances past the input buffer boundary. [ 94.984676] ================================================================== [ 94.985301] BUG: KASAN: slab-out-of-bounds in aa_dfa_match+0x5ae/0x760 [ 94.985655] Read of size 1 at addr ffff888100342000 by task file/976 [ 94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy) [ 94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 94.986329] Call Trace: [ 94.986341] <TASK> [ 94.986347] dump_stack_lvl+0x5e/0x80 [ 94.986374] print_report+0xc8/0x270 [ 94.986384] ? aa_dfa_match+0x5ae/0x760 [ 94.986388] kasan_report+0x118/0x150 [ 94.986401] ? aa_dfa_match+0x5ae/0x760 [ 94.986405] aa_dfa_match+0x5ae/0x760 [ 94.986408] __aa_path_perm+0x131/0x400 [ 94.986418] aa_path_perm+0x219/0x2f0 [ 94.986424] apparmor_file_open+0x345/0x570 [ 94.986431] security_file_open+0x5c/0x140 [ 94.986442] do_dentry_open+0x2f6/0x1120 [ 94.986450] vfs_open+0x38/0x2b0 [ 94.986453] ? may_open+0x1e2/0x2b0 [ 94.986466] path_openat+0x231b/0x2b30 [ 94.986469] ? __x64_sys_openat+0xf8/0x130 [ 94.986477] do_file_open+0x19d/0x360 [ 94.986487] do_sys_openat2+0x98/0x100 [ 94.986491] __x64_sys_openat+0xf8/0x130 [ 94.986499] do_syscall_64+0x8e/0x660 [ 94.986515] ? count_memcg_events+0x15f/0x3c0 [ 94.986526] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986540] ? handle_mm_fault+0x1639/0x1ef0 [ 94.986551] ? vma_start_read+0xf0/0x320 [ 94.986558] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986561] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986563] ? fpregs_assert_state_consistent+0x50/0xe0 [ 94.986572] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986574] ? arch_exit_to_user_mode_prepare+0x9/0xb0 [ 94.986587] ? srso_alias_return_thunk+0x5/0xfbef5 [ 94.986588] ? irqentry_exit+0x3c/0x590 [ 94.986595] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 94.986597] RIP: 0033:0x7fda4a79c3ea Fix by extracting the character value before invoking match_char, ensuring single evaluation per outer loop.

CVSS: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Analyzed
Record last updated: Aug 5, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from 074c1cd798cb0b481d7eaa749b64aa416563c053 before c7dc56d8b37eda1396feeec3ab1c7ecee5eae31b; from 074c1cd798cb0b481d7eaa749b64aa416563c053 before f16f2e5936c0f5f0d11fdf10d2be3e47e7108e42; 074c1cd798cb0b481d7eaa749b64aa416563c053 builds before 1fc94f16098213d01e56c97feed9b3ecf0147a37; 074c1cd798cb0b481d7eaa749b64aa416563c053 builds before 5a184f7cbdeaad17e16dedf3c17d0cd622edfed8; from 074c1cd798cb0b481d7eaa749b64aa416563c053 before b73c1dff8a9d7eeaebabf8097a5b2de192f40913; from 074c1cd798cb0b481d7eaa749b64aa416563c053 before 0510d1ba0976f97f521feb2b75b0572ea5df3ceb; from 074c1cd798cb0b481d7eaa749b64aa416563c053 before 383b7270faf42564f133134c2fc3c24bbae52615; from 074c1cd798cb0b481d7eaa749b64aa416563c053 before 8756b68edae37ff546c02091989a4ceab3f20abd	CNA record
linux linux_kernel linux:linux_kernel	from 4.17.1 before 5.10.253; from 5.11 before 5.15.203; from 5.16 before 6.1.169; from 6.2 before 6.6.130; from 6.7 before 6.12.77; from 6.13 before 6.18.18; from 6.19 before 6.19.8; 4.17; and 7 more ranges	NVD

References

References

https://git.kernel.org/stable/c/c7dc56d8b37eda1396feeec3ab1c7ecee5eae31b	patch
https://git.kernel.org/stable/c/f16f2e5936c0f5f0d11fdf10d2be3e47e7108e42	patch
https://git.kernel.org/stable/c/1fc94f16098213d01e56c97feed9b3ecf0147a37	patch
https://git.kernel.org/stable/c/5a184f7cbdeaad17e16dedf3c17d0cd622edfed8	patch
https://git.kernel.org/stable/c/b73c1dff8a9d7eeaebabf8097a5b2de192f40913	patch
https://git.kernel.org/stable/c/0510d1ba0976f97f521feb2b75b0572ea5df3ceb	patch
https://git.kernel.org/stable/c/383b7270faf42564f133134c2fc3c24bbae52615	patch
https://git.kernel.org/stable/c/8756b68edae37ff546c02091989a4ceab3f20abd	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.