* [CVE-2026-97589][MODERATE 7.0] s390/crypto: Fix wrong return code to engine in asynch callbacks
@ 2026-09-26 19:43 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-26 19:43 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97589
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: s390/crypto: Fix wrong return code to engine in asynch callbacks
Commit: 972e0d9b7d1d112240ccde1f1be85bf9ffaa1720
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=972e0d9b7d1d112240ccde1f1be85bf9ffaa1720
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97589
Analysis date: Sat, 26 Sep 2026 15:43:33 -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-2026-97589 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97589
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-2026-97589 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-97589 CHECK WITH IMPACT FROM ORIG NN LOW 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-675;*CWE-416;CWE-415;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'The s390 protected key AES and PHMAC do_one_request callbacks explicitly finalize an asynchronous crypto request but return the negative operation result to the crypto engine. The engine can interpret this return value as a failure to take ownership and complete the same request for a second time. The first completion callback may release the request or related state before the second completion accesses it, creating a potential use after free or double free condition. For the CVSS the PR:L value is used because a local user or process must access the affected crypto algorithm and submit an operation that reaches an error path. The issue is not directly network reachable. Impact is at least a local denial of service via kernel crash and in the worst case may include confidentiality and integrity impact if the double completion produces exploitable memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) SKIP CVE-2026-97589 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE SIMPLEFIX HARDWARE LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* No floor or cap changed either score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Conservative signals:
* +2 Real UAF or active lifetime violation. The first explicit finalization invokes the completion callback, which may end the request lifetime. Returning a negative value then causes the engine to complete the same request again through its retained pointer.
* +1 Reliable kernel crash or strong DoS. Double completion can cause a stale callback invocation, duplicate cleanup, or a kernel fault.
* +1 Local unprivileged trigger. The supplied PR:L assessment and normal AF_ALG exposure support a local, below-host-admin process submitting requests to the affected algorithms and reaching an operation error.
* Total: 4.
Additional paranoid signal:
* +1 Weak exploitation leverage. The second completion is not merely a passive stale read. It obtains and invokes the completion callback through a request whose lifetime may already have ended. This is meaningful active structured-object use, although controlled replacement is not established.
* Total: 5.
Non-awarded signals:
* No +2 strong leverage. Controlled reclaim, attacker-shaped replacement contents, callback substitution, arbitrary kernel read or write, and demonstrated LPE are not established.
* No confidentiality or integrity points. A stale callback path exists, but no disclosure or unauthorized modification consequence is demonstrated.
* No remote-reachability point. The vulnerable operation is locally initiated through the crypto API.
* No repeated-release/refcount +1. The first callback may release the request, and the exact engine-held request pointer survives, but the second `crypto_request_complete()` is callback dispatch rather than a directly established second `put`, `free`, or refcount mutation.
* No paranoid repeated-refcount point for the same reason.
* FLOOR 5 was not applied under the repeated-release rule. The paranoid score reaches 5 through the distinct stale callback-dispatch concern.
* No additional Availability point. It would duplicate the same crash consequence.
* No hardware penalty. s390 protected-key support limits affected systems, but the supplied evidence does not establish a rare peripheral or unusual mode within the affected s390 deployment.
3. Reachability analysis
A local process must access an affected PAES or PHMAC crypto algorithm and submit an asynchronous operation that returns an error after explicit finalization. The supplied PR:L analysis supports below-host-admin reachability, and no host-administrator capability check is identified.
No namespace capability is required or relevant to the described crypto request path. No direct network trigger exists. Affected s390 hardware, the relevant algorithm registration, and Linux 6.16 or later are deployment prerequisites, but they are not separate attacker-controlled privileged setup stages.
This is not a race. Once the callback explicitly finalizes the request and returns a negative result, the second completion follows from crypto-engine return-value handling.
4. Primitive and severity interpretation
The exact primitive is double completion of one asynchronous crypto request. The first completion can invoke a callback that releases the request or related state. The crypto engine retains the same request pointer and invokes completion again, directly implying a possible stale post-lifetime callback access.
The request is an active structured object because the stale operation consumes its completion callback state. This is broader than a fixed stale buffer or an immediate cleanup-only pointer fault.
It is not a concrete repeated-release case under the dedicated rule. The first callback may end the lifetime, but the patched control flow directly establishes a second completion dispatch, not a second specific lifetime/refcount helper. Downstream callbacks could perform duplicate release operations, but those callback bodies are not supplied.
This is CLASS_B rather than CLASS_A. A real lifetime violation and callback-bearing stale object are present, but controlled reclaim, function-pointer replacement, arbitrary read/write, and privilege escalation are not demonstrated.
The demonstrated practical consequence is local kernel crash or DoS. Exploitable callback or replacement-object control remains unresolved rather than established. ImportantCandidate is YES because post-lifetime callback dispatch needs Important-vs-Moderate analysis. AutoDowngradeAllowed is NO because automatically treating the issue as an ordinary crash would discard a concrete active-object lifetime primitive with unresolved callback-related leverage.
5. One-sentence report phrase
Incorrect return handling after explicit s390 crypto request finalization can cause a second completion through a potentially stale request and lead to a local kernel crash or unresolved callback-related memory corruption.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Confirm the affected completion callback lifetimes, whether callbacks synchronously free requests or nested state, and whether an ordinary AF_ALG user can shape allocation or reuse between the two completions.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: s390/crypto: Fix wrong return code to engine in asynch callbacks
Commit: 972e0d9b7d1d112240ccde1f1be85bf9ffaa1720
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=972e0d9b7d1d112240ccde1f1be85bf9ffaa1720
Commit description:
When crypto_finalize_hash_request() or
crypto_finalize_skcipher_request() explicitly completes a request, the
do_one_request callback must return 0 to indicate successful
handling. Returning a negative error code causes the crypto engine to
assume the driver failed to take ownership and triggers a second
completion via crypto_request_complete(), resulting in a double
completion. This pattern occurs in paes_s390.c 4 times and once in
phmac_s390.c.
Fixed in phmac_do_one_request() and all four paes do_one_request
callbacks (ecb, cbc, ctr, xts) by returning 0 after explicit
finalization instead of propagating the error code.
Fixes: 6cd87cb ("s390/crypto: Rework protected key AES for true asynch support")
Signed-off-by: Harald Freudenberger <[email protected]>
Reviewed-by: Holger Dengler <[email protected]>
Cc: [email protected] # 6.16+
Signed-off-by: Heiko Carstens <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
arch/s390/crypto/paes_s390.c
arch/s390/crypto/phmac_s390.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=972e0d9b7d1d112240ccde1f1be85bf9ffaa1720
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97589 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97589
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:L/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: 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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