* [CVE-2026-89719][MODERATE 7.0] zram: fix out-of-bounds access in read_block_state() [ Upstream
@ 2026-09-12 9:00 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-12 9:00 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89719
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: zram: fix out-of-bounds access in read_block_state() [ Upstream
Commit: e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89719
Analysis date: Sat, 12 Sep 2026 05:00:42 -0400
ActionableScore: 5
ActionableScore lower bound: 4
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-2026-89719 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89719
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-2026-89719 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89719 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-787;CWE-119;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in zram read_block_state can calculate nr_pages from the old disksize before dev_lock is acquired. If the device is reset and reinitialized with a smaller disksize before the lock is taken, the later scan can use the stale larger bound and call slot_lock past the end of the newly allocated zram table. This is a local race condition and an out of bounds access candidate rather than a network reachable bug. For the CVSS the PR:L is used for the paranoid score because some deployments may delegate zram or debugfs control to a reduced capability root, container root, or service account rather than full host administration. Impact is at least denial of service via kernel crash and in worst case may allow confidentiality or integrity impact because slot locking past the table boundary can touch memory outside the intended allocation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES OOB DANGER SIMPLEFIX HARDWARE KPANIC NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 4
* Conservative score: 4. No floor or cap applied.
* Raw paranoid score: 5
* Paranoid score: 5. No floor or cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative signals:
* +1 Constrained kernel OOB corruption candidate. `read_block_state()` can use a stale `nr_pages` value and call `slot_lock()` past the end of the newly allocated zram table.
* +1 Memory layout invariant violation. The bug is a mismatch between the old `disksize` derived bound and the new table allocation after reset and reinitialization.
* +1 Reliable kernel crash / strong DoS. Out-of-bounds slot locking can plausibly fault or corrupt adjacent kernel memory state.
* +1 Weak exploitation leverage. The out-of-bounds access is not merely a passive read, because slot locking is a write-like lock operation and the affected index range depends on stale and new device sizing plus read position behavior.
Paranoid additional signal:
* +1 Paranoid constrained corruption concern. The stale bound can drive lock operations beyond the intended allocation, and although payload and target are constrained, the primitive is strong enough to require manual review before downgrade.
Non-awarded signals:
* RealUAF not awarded. The patch establishes stale bounds and OOB table access, not use-after-free.
* Strong corruption primitive not awarded. Controlled reclaim, arbitrary write, directed kernel write, function pointer control, or controlled object replacement is not demonstrated.
* Confidentiality and integrity bonuses not awarded separately. C/I impact is plausible only as an unresolved consequence of OOB corruption, not as an established disclosure or write primitive.
* Remote reachability not awarded. This is a local zram control/debug path, not packet or network input.
* Race penalty not applied. The issue is a race, but both sides may be repeatedly attempted and the prompt forbids subtracting merely because a race exists.
* Host-admin penalty not applied. zram reset and memory tracking access are likely privileged in real deployments, but the supplied evidence does not fully establish the complete required privilege boundary.
3. Reachability analysis
The apparent trigger requires one context reading zram block state while another context resets and reinitializes the same zram device with a smaller disk size. This is local control-plane behavior.
Ordinary unprivileged reachability is not established. In normal Linux deployments, zram device reset and debug or memory tracking interfaces are usually restricted to privileged users or system services, but the supplied patch text does not prove that host-admin-equivalent privilege is required for the complete vulnerable sequence. Therefore `HostAdminRequired=UNKNOWN` is used rather than assuming either host root or ordinary user reachability.
No namespace-scoped trigger is established. There is no evidence that the complete reset, reinitialization, and `read_block_state()` access path can be performed inside attacker-created namespaces.
No direct prior public-network exposure exists. No special physical hardware is required beyond zram support. The race is timing-dependent, but the operations are plausibly repeatable if the attacker can access the relevant local interfaces.
4. Primitive and severity interpretation
The exact primitive is a stale bound race leading to out-of-bounds access on the zram table. `nr_pages` was computed before `dev_lock`, then the device could be reset and reinitialized with a smaller table before the lock was acquired. The later loop could then call `slot_lock()` on an index that is valid for the old table size but out of bounds for the new table.
This is active kernel table state rather than fixed stale storage. It is not a cleanup-only stale dereference. It is not a concrete repeated release or refcount mutation. It is also not a proven UAF.
The demonstrated consequence is local kernel memory corruption risk and likely DoS. The speculative consequence is stronger exploitation from OOB lock-bit manipulation near the zram table allocation, but no controlled target, controlled payload, reclaim primitive, arbitrary read/write, or LPE chain is established.
PrimitiveClass is `CLASS_B` because a real kernel OOB corruption candidate exists, but strong Class A exploitation leverage is not established. ImportantCandidate is `YES` because this should not be automatically downgraded as an ordinary crash-only bug before manual review of the actual `slot_lock()` operation, table layout, allocator behavior, and interface permissions. AutoDowngradeAllowed is `NO` because a concrete kernel OOB write-like primitive with unresolved exploitation leverage remains.
5. One-sentence report phrase
A race in zram `read_block_state()` can use a stale page count after device reset and reinitialization, causing `slot_lock()` to operate past the end of the newly allocated zram table and creating a local OOB kernel access with DoS impact and unresolved corruption leverage.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: the bug is not just a warning or resource leak. It is a race leading to out-of-bounds access in kernel memory, with a write-like slot locking operation outside the intended table bounds.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: zram: fix out-of-bounds access in read_block_state() [ Upstream
Commit: e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
Changed files:
drivers/block/zram/zram_drv.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=e7dbcb7a561a21e9a8f5b5fa90bb95aefbd0739d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89719 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89719
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:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
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: 4
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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