CVE-2026-23406 (GCVE-0-2026-23406)
Vulnerability from cvelistv5 – Published: 2026-04-01 08:36 – Updated: 2026-04-02 14:44
VLAI?
Title
apparmor: fix side-effect bug in match_char() macro usage
Summary
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.
Severity ?
7.8 (High)
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Affected:
074c1cd798cb0b481d7eaa749b64aa416563c053 , < 5a184f7cbdeaad17e16dedf3c17d0cd622edfed8
(git)
Affected: 074c1cd798cb0b481d7eaa749b64aa416563c053 , < b73c1dff8a9d7eeaebabf8097a5b2de192f40913 (git) Affected: 074c1cd798cb0b481d7eaa749b64aa416563c053 , < 0510d1ba0976f97f521feb2b75b0572ea5df3ceb (git) Affected: 074c1cd798cb0b481d7eaa749b64aa416563c053 , < 383b7270faf42564f133134c2fc3c24bbae52615 (git) Affected: 074c1cd798cb0b481d7eaa749b64aa416563c053 , < 8756b68edae37ff546c02091989a4ceab3f20abd (git) |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"security/apparmor/match.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "5a184f7cbdeaad17e16dedf3c17d0cd622edfed8",
"status": "affected",
"version": "074c1cd798cb0b481d7eaa749b64aa416563c053",
"versionType": "git"
},
{
"lessThan": "b73c1dff8a9d7eeaebabf8097a5b2de192f40913",
"status": "affected",
"version": "074c1cd798cb0b481d7eaa749b64aa416563c053",
"versionType": "git"
},
{
"lessThan": "0510d1ba0976f97f521feb2b75b0572ea5df3ceb",
"status": "affected",
"version": "074c1cd798cb0b481d7eaa749b64aa416563c053",
"versionType": "git"
},
{
"lessThan": "383b7270faf42564f133134c2fc3c24bbae52615",
"status": "affected",
"version": "074c1cd798cb0b481d7eaa749b64aa416563c053",
"versionType": "git"
},
{
"lessThan": "8756b68edae37ff546c02091989a4ceab3f20abd",
"status": "affected",
"version": "074c1cd798cb0b481d7eaa749b64aa416563c053",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"security/apparmor/match.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.17"
},
{
"lessThan": "4.17",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.130",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.77",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.18",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.8",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0-rc4",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.130",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.77",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.18",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.8",
"versionStartIncluding": "4.17",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0-rc4",
"versionStartIncluding": "4.17",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix side-effect bug in match_char() macro usage\n\nThe match_char() macro evaluates its character parameter multiple\ntimes when traversing differential encoding chains. When invoked\nwith *str++, the string pointer advances on each iteration of the\ninner do-while loop, causing the DFA to check different characters\nat each iteration and therefore skip input characters.\nThis results in out-of-bounds reads when the pointer advances past\nthe input buffer boundary.\n\n[ 94.984676] ==================================================================\n[ 94.985301] BUG: KASAN: slab-out-of-bounds in aa_dfa_match+0x5ae/0x760\n[ 94.985655] Read of size 1 at addr ffff888100342000 by task file/976\n\n[ 94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy)\n[ 94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n[ 94.986329] Call Trace:\n[ 94.986341] \u003cTASK\u003e\n[ 94.986347] dump_stack_lvl+0x5e/0x80\n[ 94.986374] print_report+0xc8/0x270\n[ 94.986384] ? aa_dfa_match+0x5ae/0x760\n[ 94.986388] kasan_report+0x118/0x150\n[ 94.986401] ? aa_dfa_match+0x5ae/0x760\n[ 94.986405] aa_dfa_match+0x5ae/0x760\n[ 94.986408] __aa_path_perm+0x131/0x400\n[ 94.986418] aa_path_perm+0x219/0x2f0\n[ 94.986424] apparmor_file_open+0x345/0x570\n[ 94.986431] security_file_open+0x5c/0x140\n[ 94.986442] do_dentry_open+0x2f6/0x1120\n[ 94.986450] vfs_open+0x38/0x2b0\n[ 94.986453] ? may_open+0x1e2/0x2b0\n[ 94.986466] path_openat+0x231b/0x2b30\n[ 94.986469] ? __x64_sys_openat+0xf8/0x130\n[ 94.986477] do_file_open+0x19d/0x360\n[ 94.986487] do_sys_openat2+0x98/0x100\n[ 94.986491] __x64_sys_openat+0xf8/0x130\n[ 94.986499] do_syscall_64+0x8e/0x660\n[ 94.986515] ? count_memcg_events+0x15f/0x3c0\n[ 94.986526] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 94.986540] ? handle_mm_fault+0x1639/0x1ef0\n[ 94.986551] ? vma_start_read+0xf0/0x320\n[ 94.986558] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 94.986561] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 94.986563] ? fpregs_assert_state_consistent+0x50/0xe0\n[ 94.986572] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 94.986574] ? arch_exit_to_user_mode_prepare+0x9/0xb0\n[ 94.986587] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 94.986588] ? irqentry_exit+0x3c/0x590\n[ 94.986595] entry_SYSCALL_64_after_hwframe+0x76/0x7e\n[ 94.986597] RIP: 0033:0x7fda4a79c3ea\n\nFix by extracting the character value before invoking match_char,\nensuring single evaluation per outer loop."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-04-02T14:44:35.415Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/5a184f7cbdeaad17e16dedf3c17d0cd622edfed8"
},
{
"url": "https://git.kernel.org/stable/c/b73c1dff8a9d7eeaebabf8097a5b2de192f40913"
},
{
"url": "https://git.kernel.org/stable/c/0510d1ba0976f97f521feb2b75b0572ea5df3ceb"
},
{
"url": "https://git.kernel.org/stable/c/383b7270faf42564f133134c2fc3c24bbae52615"
},
{
"url": "https://git.kernel.org/stable/c/8756b68edae37ff546c02091989a4ceab3f20abd"
}
],
"title": "apparmor: fix side-effect bug in match_char() macro usage",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-23406",
"datePublished": "2026-04-01T08:36:36.460Z",
"dateReserved": "2026-01-13T15:37:46.013Z",
"dateUpdated": "2026-04-02T14:44:35.415Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-23406\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-01T09:16:16.327\",\"lastModified\":\"2026-04-02T15:16:33.503\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\napparmor: fix side-effect bug in match_char() macro usage\\n\\nThe match_char() macro evaluates its character parameter multiple\\ntimes when traversing differential encoding chains. When invoked\\nwith *str++, the string pointer advances on each iteration of the\\ninner do-while loop, causing the DFA to check different characters\\nat each iteration and therefore skip input characters.\\nThis results in out-of-bounds reads when the pointer advances past\\nthe input buffer boundary.\\n\\n[ 94.984676] ==================================================================\\n[ 94.985301] BUG: KASAN: slab-out-of-bounds in aa_dfa_match+0x5ae/0x760\\n[ 94.985655] Read of size 1 at addr ffff888100342000 by task file/976\\n\\n[ 94.986319] CPU: 7 UID: 1000 PID: 976 Comm: file Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy)\\n[ 94.986322] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\\n[ 94.986329] Call Trace:\\n[ 94.986341] \u003cTASK\u003e\\n[ 94.986347] dump_stack_lvl+0x5e/0x80\\n[ 94.986374] print_report+0xc8/0x270\\n[ 94.986384] ? aa_dfa_match+0x5ae/0x760\\n[ 94.986388] kasan_report+0x118/0x150\\n[ 94.986401] ? aa_dfa_match+0x5ae/0x760\\n[ 94.986405] aa_dfa_match+0x5ae/0x760\\n[ 94.986408] __aa_path_perm+0x131/0x400\\n[ 94.986418] aa_path_perm+0x219/0x2f0\\n[ 94.986424] apparmor_file_open+0x345/0x570\\n[ 94.986431] security_file_open+0x5c/0x140\\n[ 94.986442] do_dentry_open+0x2f6/0x1120\\n[ 94.986450] vfs_open+0x38/0x2b0\\n[ 94.986453] ? may_open+0x1e2/0x2b0\\n[ 94.986466] path_openat+0x231b/0x2b30\\n[ 94.986469] ? __x64_sys_openat+0xf8/0x130\\n[ 94.986477] do_file_open+0x19d/0x360\\n[ 94.986487] do_sys_openat2+0x98/0x100\\n[ 94.986491] __x64_sys_openat+0xf8/0x130\\n[ 94.986499] do_syscall_64+0x8e/0x660\\n[ 94.986515] ? count_memcg_events+0x15f/0x3c0\\n[ 94.986526] ? srso_alias_return_thunk+0x5/0xfbef5\\n[ 94.986540] ? handle_mm_fault+0x1639/0x1ef0\\n[ 94.986551] ? vma_start_read+0xf0/0x320\\n[ 94.986558] ? srso_alias_return_thunk+0x5/0xfbef5\\n[ 94.986561] ? srso_alias_return_thunk+0x5/0xfbef5\\n[ 94.986563] ? fpregs_assert_state_consistent+0x50/0xe0\\n[ 94.986572] ? srso_alias_return_thunk+0x5/0xfbef5\\n[ 94.986574] ? arch_exit_to_user_mode_prepare+0x9/0xb0\\n[ 94.986587] ? srso_alias_return_thunk+0x5/0xfbef5\\n[ 94.986588] ? irqentry_exit+0x3c/0x590\\n[ 94.986595] entry_SYSCALL_64_after_hwframe+0x76/0x7e\\n[ 94.986597] RIP: 0033:0x7fda4a79c3ea\\n\\nFix by extracting the character value before invoking match_char,\\nensuring single evaluation per outer loop.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0510d1ba0976f97f521feb2b75b0572ea5df3ceb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/383b7270faf42564f133134c2fc3c24bbae52615\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5a184f7cbdeaad17e16dedf3c17d0cd622edfed8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8756b68edae37ff546c02091989a4ceab3f20abd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b73c1dff8a9d7eeaebabf8097a5b2de192f40913\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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