[CVE-2026-63805][MODERATE 7.0] crypto: nx - fix nx_crypto_ctx_exit argument

[CVE-2026-63805][MODERATE 7.0] crypto: nx - fix nx_crypto_ctx_exit argument

[AL-KERNEL]

CVE: CVE-2026-63805
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: crypto: nx - fix nx_crypto_ctx_exit argument
Commit: 8d8507a457667f23477a15496b91908a5b5b7cf3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d8507a457667f23477a15496b91908a5b5b7cf3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63805
Analysis date: Sun, 19 Jul 2026 10:58:24 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local AF_ALG user can trigger a type confusion in the crypto nx context cleanup path during Crypto API object destruction, causing a kernel oops and raising a weak but review-worthy memory corruption concern.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-63805 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63805

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-2026-63805	MODERATE	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-843;CWE-763;**CWE-476;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A type confusion in the crypto nx context cleanup path can occur because nx_crypto_ctx_exit() treated an nx_crypto_ctx pointer as a crypto_tfm pointer and then derived a bogus context with crypto_tfm_ctx(). This can make the driver free or access memory through an invalid kernel pointer during Crypto API object destruction, producing an oops when AF_ALG userspace closes the affected transform. For the CVSS the PR:L is used because a local user or local process is needed to create and release the AF_ALG crypto object, but full administrative privileges are not necessarily required. The issue is not network reachable by itself and depends on the nx crypto driver and affected algorithms being available on the system. Impact is at least local denial of service via kernel crash. In the paranoid interpretation, the bug class is type confusion with invalid free or wrong object access, so memory corruption and privilege escalation risk should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	DANGER INIT LINUS KPANIC 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The observed call trace comes from AF_ALG release from userspace, and AF_ALG crypto sockets are commonly reachable by local unprivileged processes unless restricted by policy.
* Memory corruption, weak/indirect corruption candidate: +1. The bug is a type confusion / bogus struct interpretation where an nx_crypto_ctx pointer is treated as crypto_tfm and then passed through crypto_tfm_ctx().
* Reliable kernel crash / strong DoS: +1. The commit includes a real kernel oops from bad kernel memory access during crypto object destruction.
* Local unprivileged high-control kernel data-plane API refinement: +1. AF_ALG lets local users create and destroy Crypto API objects and influence transform lifetime paths.

Paranoid additional signal:

* Weak LPE concern: +1. The cleanup path can operate on a bogus derived context and may call kfree_sensitive() and write NULL through fields of an incorrectly interpreted object. This is not a demonstrated exploit primitive, but it is more serious than a plain NULL dereference.

Negative / limiting factors:

* Hardware / configuration dependency: -1 considered for conservative interpretation. The affected nx crypto driver depends on specific hardware / driver availability and affected algorithms being exposed.
* No remote reachability: 0. This is not network-triggerable by itself.
* No strong LPE primitive: 0. The patch does not show attacker-controlled reclaim, controlled overwrite, callback control, or arbitrary write.

## 3. Reachability analysis

A local process can potentially trigger the bug by creating and releasing AF_ALG crypto objects that use the affected nx backend. The trace shows the failure during socket close and Crypto API transform destruction, so this is a local userspace reachable lifetime / cleanup path rather than a privileged driver initialization path.

Namespaces and containers can matter because AF_ALG may be available inside containers unless blocked by seccomp, LSM, or container runtime policy. This does not require full host root in the generic Linux model, but practical reachability depends on whether the nx algorithms are registered and visible to the attacker.

The path is not remotely reachable unless an application exposes an AF_ALG-backed crypto operation to remote input and performs object creation / teardown on behalf of the attacker, which is not inherent to the kernel bug.

Call-site confidence: medium. The provided trace shows the relevant destruction path through AF_ALG and Crypto API, but the full set of nx shash / skcipher callers is not included.

## 4. Severity interpretation

This behaves above an ordinary Moderate because it is not just validation or a warning. It is a real type confusion in a cleanup path with an observed kernel oops and possible wrong-object cleanup.

Realistic impact is local denial of service on systems with the affected nx crypto backend available. Theoretical impact includes memory corruption concerns because the wrong context can be used for freeing sensitive memory and clearing fields, but the patch does not demonstrate a controlled overwrite, UAF reclaim, or reliable privilege escalation path.

Therefore, conservative handling is Borderline / manual review recommended, while paranoid handling reaches Actionable Moderate and should not be auto-closed without review.

## 5. One-sentence report phrase

A local AF_ALG user can trigger a type confusion in the crypto nx context cleanup path during Crypto API object destruction, causing a kernel oops and raising a weak but review-worthy memory corruption concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug is a type confusion / wrong-object cleanup issue in a local unprivileged AF_ALG reachable path, with an observed crash and a plausible weak memory corruption concern even though practical privilege escalation is not demonstrated.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: crypto: nx - fix nx_crypto_ctx_exit argument
Commit: 8d8507a457667f23477a15496b91908a5b5b7cf3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8d8507a457667f23477a15496b91908a5b5b7cf3

Commit description:

nx_crypto_ctx_shash_exit calls nx_crypto_ctx_exit with crypto_shash_ctx(...)
but crypto_shash_ctx gives a nx_crypto_ctx *, not a crypto_tfm *.

Fix the type in nx_crypto_ctx_exit and drop the bogus crypto_tfm_ctx
call.

This fixes the following oops:

  BUG: Unable to handle kernel data access at 0xc0403effffffffc8
  Faulting instruction address: 0xc000000000396cb4
  Oops: Kernel access of bad area, sig: 11 [#15]
  Call Trace:
   nx_crypto_ctx_shash_exit+0x24/0x60
   crypto_shash_exit_tfm+0x28/0x40
   crypto_destroy_tfm+0x98/0x140
   crypto_exit_ahash_using_shash+0x20/0x40
   crypto_destroy_tfm+0x98/0x140
   hash_release+0x1c/0x30
   alg_sock_destruct+0x38/0x60
   __sk_destruct+0x48/0x2b0
   af_alg_release+0x58/0xb0
   __sock_release+0x68/0x150
   sock_close+0x20/0x40
   __fput+0x110/0x3a0
   sys_close+0x48/0xa0
   system_call_exception+0x140/0x2d0
   system_call_common+0xf4/0x258

.. which came from hardlink(1) opportunistically using AF_ALG.

The same problem exists with nx_crypto_ctx_skcipher_exit getting a context
it wasn't expecting, but apparently nobody hit that for years.

Cc: Eric Biggers <ebiggers@kernel.org>
Cc: stable@vger.kernel.org
Fixes: bfd9efd ("crypto: nx - convert AES-ECB to skcipher API")
Fixes: 9420e62 ("crypto: nx - Use API partial block handling")
Acked-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Reported-by: Calvin Buckley <calvin@cmpct.info>
Tested-by: Calvin Buckley <calvin@cmpct.info>
Suggested-by: Brad Spengler <brad.spengler@opensrcsec.com>
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/crypto/nx/nx.c
  drivers/crypto/nx/nx.h

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=8d8507a457667f23477a15496b91908a5b5b7cf3

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-63805 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63805

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: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: 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
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My contact email for such notifications is alexanjelausa@gmail.com (and both
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