* [CVE-2026-80864][IMPORTANT] RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp [ Upstream
@ 2026-09-04 20:47 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-04 20:47 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-80864
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp [ Upstream
Commit: 0136b528b753c5a56e4d997ef20b86bb6750b8fb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0136b528b753c5a56e4d997ef20b86bb6750b8fb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80864
Analysis date: Fri, 04 Sep 2026 16:47:29 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES
Summary:
A local user with access to RXE RDMA QP modification can race `IB_QP_MAX_DEST_RD_ATOMIC` updates against the live responder task, causing a confirmed use-after-free in `rxe_receiver()` and at least a local kernel crash, with possible higher impact requiring manual review.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80864 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80864
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: IMPORTANT
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-2026-80864 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-80864 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-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'RDMA rxe has a race in rxe_qp_from_attr() when IB_QP_MAX_DEST_RD_ATOMIC is modified without holding the responder state lock while rxe_receiver() can still walk qp resp resources. A local user with access to the rxe RDMA device can race modify_qp() against responder processing so the rd_atomic resources array is freed and replaced while rxe_prepare_res() or find_resource() still uses it, resulting in a slab use-after-free. For the CVSS the PR:L is used because reliable triggering requires local code execution and access to RDMA userspace interfaces, but not full host administrator privileges in deployments where rxe is available to users. The issue is not directly network reachable by packet traffic alone, although peer traffic may help keep the responder path active. Impact is at least local denial of service via kernel crash and in the paranoid case may include confidentiality and integrity impact because the primitive is kernel use-after-free memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) YES DANGER NOMEMCHK RACE UAF NETWORK LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
## 1. ActionableScore
* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::
## 2. Signal breakdown
Conservative signals:
* Local unprivileged trigger: +1. The commit explicitly states that a local unprivileged user can race `modify_qp()` against the responder path when RXE is available.
* Memory corruption, weak race-UAF primitive: +1. This is a confirmed slab use-after-free, but the patch does not show attacker-controlled reclaim, arbitrary overwrite, callback control, or type confusion.
* Real lifetime corruption: +1. `qp->resp.resources` is freed and reallocated while `rxe_receiver()` may still walk it, and `qp->resp.res` could remain dangling.
* Reliable kernel crash / strong DoS: +1. The issue was reproduced under KASAN and described as local DoS.
Paranoid additional signal:
* Weak LPE concern: +1. The primitive is a real kernel UAF in a reachable RDMA object lifetime path, with attacker-controlled timing through `modify_qp()`, so manual review is justified even though no concrete reclaim or write primitive is demonstrated.
Not counted:
* Remote reachable: +0. Packet traffic may help keep the responder path active, but the key trigger is local `modify_qp()`.
* Strong LPE plausibility: +0. No demonstrated controlled reclaim, overwrite, refcount takeover, function pointer control, or object confusion.
* Hard race penalty: 0. Although this is a race, it is reproduced and appears naturally triggerable through concurrent QP modification and responder activity.
## 3. Reachability analysis
The bug is reachable by a local user that can access the RXE RDMA device and issue QP modification operations. It does not require full host administrator privileges in deployments where Soft RoCE / RXE and RDMA userspace access are available to ordinary users or service accounts. Namespaces and device-cgroup policy matter: if `/dev/infiniband/*` or RXE setup is restricted to administrators, practical reachability is lower, but the commit text supports local unprivileged triggering in at least some configurations. The path is not directly network-triggerable by packets alone, although remote peer activity can help exercise the responder task.
## 4. Severity interpretation
This is more than an ordinary Moderate because it is a confirmed kernel UAF race, not merely a NULL dereference or resource leak. Realistic demonstrated impact is local kernel crash / DoS. Theoretical escalation risk exists because the stale pointer targets heap-backed RDMA responder resources, but the patch does not show a strong exploitation primitive such as attacker-controlled reclaim or arbitrary write. Therefore the conservative score is borderline/manual-review, while the paranoid score is Actionable Moderate and should not be auto-closed.
## 5. One-sentence report phrase
A local user with access to RXE RDMA QP modification can race `IB_QP_MAX_DEST_RD_ATOMIC` updates against the live responder task, causing a confirmed use-after-free in `rxe_receiver()` and at least a local kernel crash, with possible higher impact requiring manual review.
## 6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: this is a confirmed kernel UAF race in a local userspace-reachable RDMA object lifetime path, and the paranoid score reaches the actionable range even though practical LPE is not demonstrated.
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp [ Upstream
Commit: 0136b528b753c5a56e4d997ef20b86bb6750b8fb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0136b528b753c5a56e4d997ef20b86bb6750b8fb
Changed files:
drivers/infiniband/sw/rxe/rxe_qp.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=0136b528b753c5a56e4d997ef20b86bb6750b8fb
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-80864 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80864
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:L/UI:N/S:U/C:N/I:N/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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT
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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2026-09-04 20:47 21% [CVE-2026-80864][IMPORTANT] RDMA/rxe: Fix responder UAF on IB_QP_MAX_DEST_RD_ATOMIC modify_qp [ Upstream AL-KERNEL
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