* [CVE-2026-99059][IMPORTANT] wireguard: noise: reject response consumption after intermediate initiation
@ 2026-10-27 4:38 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 4:38 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99059
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: wireguard: noise: reject response consumption after intermediate initiation
Commit: fb5ce4c7790c3eeec820302d08d70ecf46af4295
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb5ce4c7790c3eeec820302d08d70ecf46af4295
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99059
Analysis date: Tue, 27 Oct 2026 00:38:12 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A precisely timed replay race can overwrite a newer WireGuard handshake with stale cryptographic state and derive a duplicate session, creating unresolved key/nonce-reuse security impact.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99059 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99059
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-2026-99059 IMPORTANT https://www.kernelcve.org/list/?q=CVE-2026-99059 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L';CWE-362;CWE-367;CWE-323;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L';BEST CVSS score: '7.7';DESCR 'A race in WireGuard response processing can allow two threads to consume the same valid response around an intervening handshake initiation. The later thread can overwrite the newer handshake state and establish a second session using the same cryptographic state as the first session. If both sessions process traffic with independently restarted counters, reuse of a traffic key and nonce may expose plaintext relationships, permit packet forgery, or disrupt tunnel traffic, although the required three thread ordering is described as extremely difficult to achieve in practice. For the CVSS the PR:N value is selected because a network attacker does not need an authenticated local account, but must be able to replay a valid observed response to a reachable WireGuard UDP endpoint with precise timing. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7.7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were TEMP_KPANIC_MERGE_IMPORTANT_WINS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS unavailable and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) MAYBE WRITE OOB LOCK INIT NETWORK LINUS TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base 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
* +2 Remote network reachability: replay of a valid response to a reachable WireGuard UDP endpoint can enter the vulnerable response-consumption path.
* +1 Active structured-state corruption: thread B copies stale handshake crypto state over a newer initiation and changes the handshake state to response-consumed.
* +1 Practical chain: the commit explicitly traces stale-state installation into `derive_session()`, producing a second session from the same cryptographic state.
* +1 Integrity concern: duplicate session/key-and-counter state violates WireGuard’s cryptographic session uniqueness invariant and plausibly permits forged or disrupted traffic.
* -1 Hard timing: the required three-thread ordering and slow-crypto/write-lock interleaving are explicitly described as essentially impossible to hit meaningfully in practice.
* Paranoid +1 confidentiality concern: independently restarted counters under the same traffic key credibly imply nonce reuse and possible plaintext-relation exposure, but concrete plaintext recovery is not shown.
No UAF, heap OOB, arbitrary write, controlled reclaim, kernel-memory disclosure, LPE, or reliable crash is shown. Confidentiality is therefore scored only in the paranoid reading.
3. Reachability analysis
The assessed actor is a remote, non-authenticated local-account attacker able to observe and replay a valid WireGuard response with precise timing. No host UID 0, capability, namespace privilege, prior privileged setup, or special hardware is required for the packet trigger. The race is remotely invocable but exceptionally difficult to win.
4. Primitive and severity reading
The write is the stale `memcpy()` into `handshake->crypto`, followed by `handshake->state = 2`. The privileged later consumer is `derive_session()`, which installs operational tunnel session state. The trust boundary is the remote peer/network-to-kernel WireGuard cryptographic state boundary.
This is CLASS_B active structured-state corruption, not memory corruption. Duplicate session derivation is shown; practical packet forgery, plaintext recovery, or tunnel compromise remains unproven. The specific corrupt-and-consume chain makes this an Important candidate under mandatory manual review, despite the severe timing constraint. Auto-downgrade is unsafe because the non-crash cryptographic integrity consequence remains unresolved.
This is not an authorization DENY-to-ALLOW bug, so B4-PENDING does not apply.
5. One-sentence report phrase
A precisely timed replay race can overwrite a newer WireGuard handshake with stale cryptographic state and derive a duplicate session, creating unresolved key/nonce-reuse security impact.
6. Manual review advice
MANUAL CHECK REQUIRED
The patch proves active cryptographic-state overwrite followed by session derivation across a remote trust boundary, while the practical confidentiality and forgery consequences remain unresolved.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: wireguard: noise: reject response consumption after intermediate initiation
Commit: fb5ce4c7790c3eeec820302d08d70ecf46af4295
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb5ce4c7790c3eeec820302d08d70ecf46af4295
Commit description:
Two threads begin processing the identical response message, received
twice. The first thread, A, runs. While it's running, the second one,
B, gets partway through, and during that slow calculation, or even while
blocking on down_write(), A completes and then also a handshake
initiation that's already been queued up runs in thread C, which itself
takes that same down_write(). The handshake initiation creation
succeeds, and sets the state back to waiting-for-response, and calls
up_write(), at which point thread B resumes, because either its finished
its calculations or was finally allowed to acquire down_write(). Thread
B then copies the state back to the peer, and begins a new session,
using that state, which is the same session as the one made in thread A.
Thread A Thread B Thread C
down_read()
sA = handshake->state
memcpy(cA, handshake->crypto)
up_read()
if (sA != 1)
goto fail
slow_crypto(cA)
down_read()
sB = handshake->state
memcpy(cB, handshake->crypto)
up_read()
if (sB != 1)
goto fail
slow_crypto(cB)
down_write()
if (sA != handshake->state)
goto fail
memcpy(handshake->crypto, cA)
handshake->state = 2
up_write()
down_write()
if (handshake->state != 2)
goto fail
derive_session(handshake->crypto)
up_write()
down_write()
slow_crypto(handshake->crypto)
handshake->state = 1
up_write()
down_write()
if (sB != handshake->state)
goto fail
memcpy(handshake->crypto, cB)
handshake->state = 2
up_write()
down_write()
if (handshake->state != 2)
goto fail
derive_session(handshake->crypto)
up_write()
This seems basically impossible to hit in a meaningful way in practice,
but ensure that it absolutely cannot happen by comparing the ephemeral
private key that's on the stack with the latest one that the peer's
handshake state has.
Cc: [email protected]
Fixes: e7096c1 ("net: WireGuard secure network tunnel")
Reported-by: Jérémy Jean <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/net/wireguard/noise.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=fb5ce4c7790c3eeec820302d08d70ecf46af4295
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99059 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99059
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:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
The Best / paranoid CVSS score: 7.7
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: NO
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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