* [CVE-2022-49907][LOW] net: mdio: fix undefined behavior in bit shift for __mdiobus_register [ Upstream
@ 2026-10-13 0:48 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-13 0:48 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2022-49907
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: mdio: fix undefined behavior in bit shift for __mdiobus_register [ Upstream
Commit: 20ed01a7b9af6e6a3c33761eebbb710ea6dd49b7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=20ed01a7b9af6e6a3c33761eebbb710ea6dd49b7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-49907
Analysis date: Mon, 12 Oct 2026 20:48:49 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2022-49907 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-49907
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: LOW
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2022-49907 LOW https://www.kernelcve.org/list/?q=CVE-2022-49907 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';CWE-758;CWE-190;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '1.9';DESCR 'A signed 32 bit value is shifted into the sign bit in __mdiobus_register when the PHY address reaches 31, which is undefined behavior in C and produces a UBSAN shift out of bounds warning. The demonstrated path occurs during MDIO bus registration and does not provide an invalid memory access, UAF, out of bounds access, information leak, or write primitive. For the CVSS the PR:H is used because reliable triggering would normally require administrative control over driver loading or MDIO bus registration. The issue is not network reachable through packet traffic. The confirmed impact is a diagnostic warning only. A paranoid interpretation allows limited availability impact if compiler handling of the undefined expression causes PHY address 31 to be scanned incorrectly, but there is no supported path to a kernel crash or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) MAYBE WRITE KASAN OOB SIMPLEFIX NETWORK CVEOUTDATED LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate / Low-like**::
2. Signal breakdown
* +0 undefined behavior: `1 << 31` shifts a signed integer into its sign bit and triggers UBSAN, but no security primitive is established.
* +0 availability: the demonstrated consequence is a UBSAN diagnostic, not a kernel crash, persistent failure, or host-wide DoS.
* +0 B5-R: there is no heap or slab OOB write, retry-accumulated index, or later consumption of corrupted state.
* +0 B3-PENDING: no shared or file-backed storage is modified.
* +0 B4-PENDING: no authorization guard or DENY-to-ALLOW transition exists.
* No UAF, invalid memory access, controlled overwrite, information disclosure, resource leak, or lifetime violation is demonstrated.
* Remote reachability, arbitrary write, confidentiality impact, integrity impact, and privilege escalation are not established.
* The paranoid possibility of an incorrect PHY mask test is too speculative and device-local to justify an ActionableScore point.
3. Reachability analysis
The demonstrated call path runs during MDIO bus registration, shown through `fixed_mdio_bus_init()` and kernel initialization. No attacker-invocable syscall, ioctl, network packet path, or namespace-scoped interface is identified.
Intentional driver or bus registration may involve host-administrative control, but the supplied evidence does not establish a complete attacker-controlled trigger. Therefore `HostAdminRequired` and `RequiresHostUID0` remain UNKNOWN rather than assuming either host-admin or below-host-admin reachability. MDIO bus registration is part of the global driver model and is not a network-namespace-scoped operation.
No special race, retry sequence, or attacker-controlled timing exists. Relevant hardware or driver initialization may be required, but this does not create a security primitive.
4. Primitive and severity interpretation
The exact defect is C undefined behavior from shifting signed integer value `1` by 31 bits. Replacing it with `BIT(i)` produces the intended unsigned bit mask.
There is no heap access beyond bounds, stale object, lifetime mutation, shared-backing write, or authorization bypass. The behavior therefore belongs to `PrimitiveClass=NONE`, not Class C memory-fault behavior.
The demonstrated result is a UBSAN warning. A compiler could theoretically handle undefined behavior unexpectedly and affect scanning of PHY address 31, but no kernel crash, memory corruption, protected-state modification, or meaningful attacker influence is supported.
`ImportantCandidate=NO` because no Important-preserving primitive exists. `AutoDowngradeAllowed=YES` because no unresolved corruption, ownership, lifetime, or security-boundary mechanism remains.
5. One-sentence report phrase
A signed shift into bit 31 in `__mdiobus_register()` causes C undefined behavior and a UBSAN warning, but the supplied evidence establishes no attacker-reachable memory corruption, authorization bypass, or meaningful security impact.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch is a type-correctness fix for a UBSAN diagnostic, with no concrete security primitive or attacker-controlled trigger.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: mdio: fix undefined behavior in bit shift for __mdiobus_register [ Upstream
Commit: 20ed01a7b9af6e6a3c33761eebbb710ea6dd49b7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=20ed01a7b9af6e6a3c33761eebbb710ea6dd49b7
Changed files:
drivers/net/phy/mdio_bus.c
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=20ed01a7b9af6e6a3c33761eebbb710ea6dd49b7
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2022-49907 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2022-49907
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:H/PR:H/UI:N/S:U/C:N/I:N/A:N
The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 1.9
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: 0
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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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