* [CVE-2022-49846][MODERATE 7.0] udf: Fix a slab-out-of-bounds write bug in udf_find_entry()
@ 2026-10-13 2:21 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-13 2:21 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2022-49846
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: udf: Fix a slab-out-of-bounds write bug in udf_find_entry()
Commit: 583fdd98d94acba1e7225e5cc29063aef0741030
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=583fdd98d94acba1e7225e5cc29063aef0741030
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-49846
Analysis date: Mon, 12 Oct 2026 22:21:25 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2022-49846 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-49846
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: MODERATE 7.0
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2022-49846 MODERATE https://www.kernelcve.org/list/?q=CVE-2022-49846 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-122;CWE-131;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'An undersized heap allocation in udf_find_entry can cause a slab out of bounds write when a crafted UDF directory entry makes the name copy length reach 255 bytes while copy_name has space for only 254 bytes. The write occurs during pathname lookup or file open processing on the mounted UDF filesystem. A local attacker may trigger a kernel crash and the confirmed heap overwrite creates a plausible risk of broader kernel memory corruption, including potential confidentiality or integrity impact, although reliable privilege escalation is not demonstrated. For the CVSS the PR:L value is used for the paranoid score because a low privileged local user may trigger lookup after a malicious UDF image has already been mounted by an automount service or another privileged component. Mounting an arbitrary image directly normally requires administrative privileges, which is reflected by PR:H in the base score. The issue is not directly network reachable. Impact is at least a local denial of service via kernel crash and in the worst defensible case may include privilege escalation through kernel heap corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE WRITE KASAN OOB DISK KERNEL_PANIC_PLUS_UAF HARDWARE CVEOUTDATED SYZBOT KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 5
* Raw paranoid score: 1
* Paranoid score: 5
* Applied conservative Manual Review Safety Floor: 1 -> 5 because an attacker-influenced kernel heap OOB write is directly confirmed.
* Applied paranoid Manual Review Safety Floor: 1 -> 5 for the same established corruption primitive. No additional speculative leverage was scored.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
* +2 Strong corruption primitive. `udf_find_entry()` allocates 254 bytes but can copy 255 attacker-influenced bytes from a malformed UDF directory entry, producing a confirmed heap OOB write.
* -1 Highly constrained corruption. The maximum overwrite is one byte beyond the requested allocation, the trace places the allocation in a 256-byte slab slot, and no adjacent active object, pointer, callback, or security-sensitive target is identified.
* Total raw score: 2 - 1 = 1.
* No reliable-crash point was awarded. KASAN detects the invalid write, but the supplied evidence does not establish a production kernel panic independently of memory-debugging instrumentation.
* No local-unprivileged point was awarded. Path lookup may be performed without privilege after mounting, but the evidence does not establish that the same below-host-admin actor can introduce and mount the crafted UDF image.
* No confidentiality, integrity-consequence, LPE, arbitrary-write, controlled-target, controlled-reclaim, or practical exploit-chain points were awarded.
* NEW52 B5-R does not apply. There is no retry-accumulated index, missing retry reset, or demonstrated later consumption of corrupted adjacent structured state.
* NEW53 B3-PENDING does not apply because no shared-backing or cross-authority write is involved.
* NEW54 B4-PENDING does not apply because there is no authorization decision or DENY-to-ALLOW transition.
* No UAF, repeated release, refcount mutation, race, RCU violation, or semantic reinterpretation exists.
3. Reachability analysis
The immediate trigger is pathname lookup or file creation on a mounted, malformed UDF filesystem. A local user may be able to invoke that lookup once the filesystem is mounted and accessible.
The supplied reproducer uses a loop device, but it does not establish who created the loop mapping or mounted the image. Mounting an arbitrary UDF image commonly involves privileged setup, while automount or removable-media workflows can separate the actor supplying the image from the actor performing the mount. The complete below-host-admin attack chain is therefore unresolved, so `HostAdminRequired=UNKNOWN` rather than YES or NO.
The evidence does not show that UDF mounting and the complete trigger are available through an attacker-created user namespace. `NamespaceScopedPrivilege` therefore remains UNKNOWN. No network trigger, race, special timing, retry sequence, or unusual physical hardware is required after the crafted filesystem has been mounted.
4. Primitive and severity interpretation
The exact primitive is a maximum one-byte heap write beyond the requested 254-byte `copy_name` allocation. The copied byte is derived from malformed filesystem data, making the write attacker-influenced. This is fixed temporary storage rather than a stale active structured object, and it is not a UAF.
The KASAN trace shows that the allocation came from `kmalloc-256`. Thus, in the observed configuration, the invalid byte enters allocator padding rather than crossing the complete 256-byte slab slot into a demonstrated adjacent object. This materially limits presently established exploitation leverage but does not negate the language-level and KASAN-confirmed heap OOB write.
No corrupted descriptor, pointer, callback, refcount, or neighboring object is shown to be consumed later. Privilege escalation and broader kernel corruption remain speculative. The issue is classified as CLASS_A because the patch directly establishes an attacker-influenced heap OOB write, but it is at the constrained end of that class.
`ImportantCandidate=YES` and `AutoDowngradeAllowed=NO` preserve the confirmed corruption primitive for human analysis. They do not assert proven Important severity or LPE. Likely operational severity is Moderate unless allocator-specific review demonstrates that the extra byte can reach meaningful adjacent state.
5. One-sentence report phrase
A malformed UDF directory entry can make `udf_find_entry()` copy 255 bytes into a 254-byte heap allocation, causing a confirmed but tightly bounded one-byte heap out-of-bounds write that requires manual exploitability review.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Confirm allocator behavior across affected configurations, whether the overflow can cross usable allocation boundaries, control of the extra byte, realistic crafted-image mounting paths, and whether any adjacent active object can be corrupted.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: udf: Fix a slab-out-of-bounds write bug in udf_find_entry()
Commit: 583fdd98d94acba1e7225e5cc29063aef0741030
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=583fdd98d94acba1e7225e5cc29063aef0741030
Commit description:
Syzbot reported a slab-out-of-bounds Write bug:
loop0: detected capacity change from 0 to 2048
==================================================================
BUG: KASAN: slab-out-of-bounds in udf_find_entry+0x8a5/0x14f0
fs/udf/namei.c:253
Write of size 105 at addr ffff8880123ff896 by task syz-executor323/3610
CPU: 0 PID: 3610 Comm: syz-executor323 Not tainted
6.1.0-rc2-syzkaller-00105-gb229b6ca5abb #0
Hardware name: Google Compute Engine/Google Compute Engine, BIOS
Google 10/11/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
print_address_description+0x74/0x340 mm/kasan/report.c:284
print_report+0x107/0x1f0 mm/kasan/report.c:395
kasan_report+0xcd/0x100 mm/kasan/report.c:495
kasan_check_range+0x2a7/0x2e0 mm/kasan/generic.c:189
memcpy+0x3c/0x60 mm/kasan/shadow.c:66
udf_find_entry+0x8a5/0x14f0 fs/udf/namei.c:253
udf_lookup+0xef/0x340 fs/udf/namei.c:309
lookup_open fs/namei.c:3391 [inline]
open_last_lookups fs/namei.c:3481 [inline]
path_openat+0x10e6/0x2df0 fs/namei.c:3710
do_filp_open+0x264/0x4f0 fs/namei.c:3740
do_sys_openat2+0x124/0x4e0 fs/open.c:1310
do_sys_open fs/open.c:1326 [inline]
__do_sys_creat fs/open.c:1402 [inline]
__se_sys_creat fs/open.c:1396 [inline]
__x64_sys_creat+0x11f/0x160 fs/open.c:1396
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7ffab0d164d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe1a7e6bb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007ffab0d164d9
RDX: 00007ffab0d164d9 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 00007ffab0cd5a10 R08: 0000000000000000 R09: 0000000000000000
R10: 00005555573552c0 R11: 0000000000000246 R12: 00007ffab0cd5aa0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Allocated by task 3610:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x3d/0x60 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:371 [inline]
__kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:380
kmalloc include/linux/slab.h:576 [inline]
udf_find_entry+0x7b6/0x14f0 fs/udf/namei.c:243
udf_lookup+0xef/0x340 fs/udf/namei.c:309
lookup_open fs/namei.c:3391 [inline]
open_last_lookups fs/namei.c:3481 [inline]
path_openat+0x10e6/0x2df0 fs/namei.c:3710
do_filp_open+0x264/0x4f0 fs/namei.c:3740
do_sys_openat2+0x124/0x4e0 fs/open.c:1310
do_sys_open fs/open.c:1326 [inline]
__do_sys_creat fs/open.c:1402 [inline]
__se_sys_creat fs/open.c:1396 [inline]
__x64_sys_creat+0x11f/0x160 fs/open.c:1396
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
The buggy address belongs to the object at ffff8880123ff800
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 150 bytes inside of
256-byte region [ffff8880123ff800, ffff8880123ff900)
The buggy address belongs to the physical page:
page:ffffea000048ff80 refcount:1 mapcount:0 mapping:0000000000000000
index:0x0 pfn:0x123fe
head:ffffea000048ff80 order:1 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00004b8500 dead000000000003 ffff888012041b40
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
[Commit description truncated; see the upstream URL below]
Changed files:
fs/udf/namei.c:253
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=583fdd98d94acba1e7225e5cc29063aef0741030
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2022-49846 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-49846
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7.8
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: unknown
Paranoid ActionableScore: 5
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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