[CVE-2026-72319][IMPORTANT] ipvs: ensure inner headers in ICMP errors are in headroom [ Upstream

[CVE-2026-72319][IMPORTANT] ipvs: ensure inner headers in ICMP errors are in headroom [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72319
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: ipvs: ensure inner headers in ICMP errors are in headroom [ Upstream
Commit: 19657b3a17b774ae4e2f2635b5ae8638c9344a40
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19657b3a17b774ae4e2f2635b5ae8638c9344a40
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72319
Analysis date: Sun, 16 Aug 2026 02:33:37 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
IPVS ICMP tunnel error handling may access inner IPv4 headers that are not present in linear skb data after `pskb_pull()`, allowing a remote sender in affected IPVS tunnel deployments to trigger invalid header access and likely kernel DoS.

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

The original Linux kernel CVE announcement for CVE-2026-72319 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72319

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-72319	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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:N/I:N/A:H';BEST CVSS score: '6.5';DESCR 'IPVS ICMP error handling for tunneled packets can access inner IPv4 headers after stripping outer headers without first ensuring that the complete inner header is present in the linear skb data. A remote sender that can deliver crafted ICMP error traffic to an IPVS node using IPIP or related tunnel handling may trigger invalid header access and a kernel crash or soft failure. For the CVSS the PR:N is used because no local user account or authentication is needed when the affected IPVS packet path is reachable from the network. AC:H is used because exploitation depends on IPVS being enabled, a tunnel based service configuration, and a packet layout that reaches the ICMP tunnel error path. Impact is primarily denial of service. For the paranoid score, the assessment stays within the invalid read class and allows limited confidentiality impact, but it does not assume an OOB write, UAF, or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 7)	YES	REMOTE NETFILTER SKB LINUS KPANIC PACKET 	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2
  Crafted ICMP error traffic can reach the affected IPVS packet path when IPVS tunnel handling is configured.

* Memory corruption, Weak/indirect corruption candidate: +1
  The bug is missing validation and missing `pskb_may_pull()` after `pskb_pull()`, causing later code to access inner IPv4 headers that may not be present in linear skb data. This is an invalid header access / limited OOB read style issue, not an OOB write or UAF.

* Reliable kernel crash / strong DoS: +1
  The affected code feeds headers into `ipv4_update_pmtu()`, `icmp_send()`, and `IP_VS_DBG()`. A malformed skb layout can plausibly cause a kernel crash or strong packet-path failure.

* Common networking core path or packet-processing path: +1
  This is in netfilter IPVS ICMP handling, i.e. kernel packet processing. It is configuration-dependent but still security-relevant when deployed.

* Confidentiality impact plausible, paranoid only: +1
  Paranoid scoring allows limited C impact because the primitive is invalid read of packet/header data in kernel context. There is no evidence of attacker-controlled disclosure, so this is not used in the conservative score.

Not counted:

* No strong generic memory corruption +2. The patch does not show OOB write, UAF, double free, type confusion, refcount takeover, or attacker-controlled overwrite.
* No privilege escalation plausible +2. No reclaim, callback control, write primitive, or object confusion is shown.
* No availability impact extra point. Strong DoS was already counted and there is no separate persistent corruption impact.

## 3. Reachability analysis

A remote sender can potentially trigger the bug by delivering crafted ICMP errors to an IPVS node that uses IPIP or related tunnel handling. No local account is needed once the affected packet path is reachable, so the practical CVSS-style privilege interpretation is PR:N for exposed deployments.

The path is not default for all Linux systems. It requires IPVS and a tunnel-based service configuration, so exploitation is environment-dependent. Configuring IPVS itself normally requires administrative privileges, but the attacker does not need those privileges if attacking an already configured load balancer.

Namespaces and containers mostly affect who can configure IPVS, not whether packets can trigger the bug after configuration. In containerized environments with delegated network administration, exposure may be easier to create, but the main risk remains network-triggered DoS against an IPVS deployment.

Call-site confidence: high. The patch directly shows the affected call path and the later users of `ip_hdr()` after skb manipulation.

## 4. Severity interpretation

This behaves more like an actionable Moderate networking bug than an ordinary low-priority cleanup. The realistic impact is remote DoS in affected IPVS tunnel deployments.

Theoretical memory corruption potential is limited to invalid header access / read-side misuse after skb headroom assumptions fail. The patch does not support a strong corruption primitive, privilege escalation, or arbitrary write. Therefore it should not be promoted to Important solely on memory-corruption grounds, but it should not be auto-closed because it is network reachable in a kernel packet-processing path.

## 5. One-sentence report phrase

IPVS ICMP tunnel error handling may access inner IPv4 headers that are not present in linear skb data after `pskb_pull()`, allowing a remote sender in affected IPVS tunnel deployments to trigger invalid header access and likely kernel DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is network reachable in configured IPVS tunnel deployments and affects kernel packet parsing. The likely impact is DoS only, but exposure depends on real IPVS tunnel configuration and should be checked manually before closure.

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

Patch: ipvs: ensure inner headers in ICMP errors are in headroom [ Upstream
Commit: 19657b3a17b774ae4e2f2635b5ae8638c9344a40
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=19657b3a17b774ae4e2f2635b5ae8638c9344a40

Changed files:
  net/netfilter/ipvs/ip_vs_core.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=19657b3a17b774ae4e2f2635b5ae8638c9344a40

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

The original Linux kernel CVE announcement for CVE-2026-72319 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72319

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:N/I:N/A:H
  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: 5
  Paranoid ActionableScore: 6

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