[CVE-2026-53268][MODERATE 7.0] netfilter: conntrack_irc: fix possible out-of-bounds read [ Upstream

[CVE-2026-53268][MODERATE 7.0] netfilter: conntrack_irc: fix possible out-of-bounds read [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53268
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: netfilter: conntrack_irc: fix possible out-of-bounds read [ Upstream
Commit: 4cdda7f868f48e2f81579371584fdbdce37df2c8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4cdda7f868f48e2f81579371584fdbdce37df2c8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53268
Analysis date: Thu, 25 Jun 2026 10:23:07 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A malformed plaintext IRC DCC payload can cause `nf_conntrack_irc` to continue parsing after a matched command fails, leading to a possible network-triggered out-of-bounds read and kernel DoS when the IRC conntrack helper is enabled.

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

The original Linux kernel CVE announcement for CVE-2026-53268 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53268

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.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-53268	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.5';DESCR 'The IRC conntrack helper can continue parsing after a DCC command string has already matched but parse_dcc fails or the command is rejected as forged. This can leave the parser in an invalid state and may lead to an out-of-bounds read while processing attacker controlled plaintext IRC traffic. For the CVSS the PR:N is used because a remote sender does not need local credentials when the nf_conntrack_irc helper inspects reachable IRC traffic. The issue is network reachable only in deployments where the IRC helper is enabled and assigned to the inspected flow, which is less common in modern TLS based IRC use. Impact is mainly denial of service through kernel packet parsing, with limited confidentiality impact possible from the invalid read class but no supported integrity impact or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE OOB SIMPLEFIX NETFILTER KPANIC 	NO	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:

* Remote reachable / network-triggerable: +2
  The affected code is in `nf_conntrack_irc`, which parses IRC traffic in the netfilter conntrack helper path. A remote peer can influence the parsed payload when the helper is enabled and assigned to the flow.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly describes a possible out-of-bounds read in kernel packet parsing. This is plausibly crashable, especially with hardened/debug kernels, although no write primitive is shown.

* Common networking / packet-processing path: +1
  The bug is in netfilter packet inspection, not a purely local ioctl or admin-only control path.

* Rare / difficult-to-reach configuration: -1
  The IRC helper is not a broad default modern exposure and plaintext IRC helper usage is uncommon in 2026 due to TLS.

* Availability impact realistic: +1
  OOB read in packet parsing can plausibly produce packet-triggered kernel fault or warning/oops behavior. This is counted conservatively as DoS risk, not as privilege escalation.

Paranoid additional signal:

* Confidentiality impact plausible: +1
  The primitive is an out-of-bounds read. No direct disclosure path is shown, so this is only limited/paranoid C:L-style concern, not a strong information leak.

Not counted:

* No integrity impact: no write, overwrite, UAF reclaim, refcount takeover, or object confusion is shown.
* No privilege escalation plausible: the patch only supports OOB read / DoS, not LPE.
* No strong generic memory corruption: this is read-only OOB, not OOB write or UAF.

## 3. Reachability analysis

The bug can be triggered by a remote sender only when `nf_conntrack_irc` is enabled and actively inspecting plaintext IRC traffic. PR:N is appropriate for the network attacker in that deployment because no local account on the firewall or gateway is required. However, the helper is configuration-dependent and likely uncommon in modern deployments because IRC is often encrypted or the helper is not auto-assigned. Containers and namespaces do not materially improve attacker reachability unless they can cause traffic to traverse a host or namespace firewall with the IRC helper enabled.

## 4. Severity interpretation

This behaves like an actionable Moderate rather than a clear Important. The network packet-processing location and OOB read make it unsuitable for automatic low-priority closure. Realistically, the most supported impact is remote DoS under specific helper configuration. Theoretical confidentiality impact is limited and not strongly demonstrated. There is no evidence of privilege escalation or integrity corruption.

## 5. One-sentence report phrase

A malformed plaintext IRC DCC payload can cause `nf_conntrack_irc` to continue parsing after a matched command fails, leading to a possible network-triggered out-of-bounds read and kernel DoS when the IRC conntrack helper is enabled.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: network-reachable kernel packet parsing plus OOB read warrants manual review, even though exposure is limited by the non-default and declining use of the IRC conntrack helper.

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

Patch: netfilter: conntrack_irc: fix possible out-of-bounds read [ Upstream
Commit: 4cdda7f868f48e2f81579371584fdbdce37df2c8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4cdda7f868f48e2f81579371584fdbdce37df2c8

Changed files:
  net/netfilter/nf_conntrack_irc.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=4cdda7f868f48e2f81579371584fdbdce37df2c8

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

The original Linux kernel CVE announcement for CVE-2026-53268 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53268

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:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 6.5

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).