Azure Linux and CVE-2024-44989: Attestation Limits and Potential Microsoft Exposures

Microsoft’s short MSRC wording that “Azure Linux includes this open‑source library and is therefore potentially affected” is accurate — but it is a scoped inventory attestation, not a technical guarantee that no other Microsoft product could contain the same vulnerable Linux kernel code. erview
CVE‑2024‑44989 is a Linux‑kernel vulnerability in the bonding driver that can produce a null‑pointer dereference in the XFRM/IPsec offload path. The problem arises from a race during bond interface changes where the driver can set the internal pointer that identifies the underlying real_dev to NULL while XFRM callbacks may run concurrently; those callbacks assume real_dev is non‑NULL and may dereference it, crashing the kernel (availability impact). The issue was reported and fixed in upstream kernel trees and later backported into multiple vendor kernels.
The technical patch series that resolved the issue refactors how xfrm offload state and device pointers are used so the races are removed and real_dev is handled safely in add/delete operations. The upstream commit(s) and the stable‑tree merges are visible in kernel patch lists and the stable tree summaries, and vendors (Red Hat, Oracle/OL, Amazon Linux, others) have incorporated fixes into their kernel advisories.
Why this matters operationally: the vulnerable code is part of the upstream Linux kernel source tree. Whether a given product is actually exposed depends on (a) whether a product includes a kernel built from an affected commit range and (b) whether the kernel was configured to enable or modularize the bonding/IPsec offload code paths in question. Those two build‑time choices make exposure an artifact‑specific property rather than a universal one for every vendor product that “uses Linux.”

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The short answer to the user’s question​

No — Azure Linux is not necessarily the only Microsoft product that could include the vulnerable open‑source code behind CVE‑2024‑44989. Microsoft has publicly attested that Azure Linux includes the implicated upstream component and is therefore potentially affected; that attestation is authoritative for Azure Linux but does not by itself prove that no other Microsoft product or image carries the same kernel code. Microsoft has stated it will expand its machine‑readable CSAF/VEX attestations (a rollout that began with Azure Linux) and will update CVE/VEX records when other Microsoft products are identified as carriers.
Put plainly: the MSRC attestation is a product‑level inventory result. Absence of a similar attestation for other Microsoft products is absence of attestation, not proof of absence.

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Why Microsoft names Azure Linux (and what that naming actually guarantees)​

What Microsoft did​

Microsoft began publishing machine‑readable CSAF and VEX attestations to make it explicit which Microsoft product artifacts include particular upstream open‑source libraries and whether those artifacts are Known Affected, Not Affected, Under Investigation, or Fixed. Their VEX rollout started with the Azure Linux distribution and includes product‑level mappings where Microsoft has completed its inventory work. The MSRC phrase “Azure Linux includes this open‑soherefore potentially affected” is precisely that — a product‑scoped inventory attestation, not an exclusivity claim.

What the attestation guarantees (and what it doesn’t)​

• What it guarantees:
• Microsoft has inspected Azure Linux images/kernels and found the implicated source or binary present in those artifacts. Customers running Azure Linux should treat these artifacts as in‑scope and follow Microsoft’s remediation guidance.
• What it does not guarantee:
• It does not mean other Microsoft products or images do not include the same code.
• It does not automatically imply Microsoft has scanned or attested WSL kernels, linux‑azure kernels, Marketplace images, container base images, or other kernel artifacts for the same CVE unless those products are explicitly named in VEX/CSAF files.

This distinction is critical for customers: treat Microsoft’s Azure Linux attestation as authoritative for Azure Linux itself, but do not assume other Microsoft‑supplied artifacts are unaffected until Microsoft publishes attestations or you verify locally.

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The technical reality: why other Microsoft artifacts could be affected​

There are several straightforward, technical reasons why the same upstream kernel defect might appear in multiple Microsoft products or artifacts:

• Kernel version selection: Microsoft builds and distributes multiple kernel artifacts (the Azure Linux distribution kernel, linux‑azure kernels for VMs, WSL2 kernel binaries and sources, and possibly tailored kernels for appliances). If any of those artifacts was built from a kernel version containing the vulnerable bonding/xfrm code, they may include the bug.
• Kernel config flags: Whether the bonding driver and its IPsec/XFRM offload code is present in a kernel depends on build‑time CONFIG flags (for example, CONFIG_BONDING and related XFRM offload options). A kernel that omits those options will not be vulnerable even if it is built from an affected source snapshot. Conversely, a kernel that enables or modules the subsystem will be.
• Modular vs built‑in: Modules can be present but not loaded; product images that ship the module may never load it depending on runtime configuration. That changes practical exposure.
• Image provenance and third‑party content: Microsoft‑published Marketplace images in Azure are often third‑party distributions (Canonical, Red Hat, SUSE, ISVs). Those images are under the image maintainer’s responsibility; Microsoft’s Azure Linux attestation does not extend to unrelated Marketplace images unless they are explicitly attested.

Because of these variables, any Microsoft artifact that ships a Linux kernel built from an affected commit range and with the relevant bonding/xfrm options enabled should be treated as potentially in scope until either Microsoft attests it as Not Affected/Fixed, or you verify the product’s kernel contents locally.

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What the upstream and vendor advisories say (quick verification)​

• NVD and vendor trackers describe CVE‑2024‑44989 as a bonding driver null‑pointer dereference stemming from setting real_dev to NULL while packets may be in transit; the fix prevents that unsafe assignment and removes the race. The NVD description confirms the vulnerability class and impact (availability/DoS).
• Kernel mailing lists and stable commit logs document the patch series and the stable‑tree merges that remedied the defect; those patches refactor xfrm state handling and the use of xso.real_dev to remove races and prevent unsafe NULL assignments. The change is present in upstream net/bonding commits and was incorporated into the stable trees and vendor kernels.
• Vendor advisories (Red Hat/Oracle/Oracle Linux, Amazon ALAS and other distributions) list the issue and indicate patched kernel updates were released for their supported kernels. These vendor advisories are the practical mechanism for customers to obtain a patched kernel from their distribution vendor.

These independent sources corroborate the technical root cause, the fix approach, and that the vulnerability was handled via kernel patching and distribution updates.

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Operational guidance: how to determine whether your Microsoft artifacts are affected​

If you operate Microsoft‑distributed images, kernels, or appliances, follow the steps below to determine exposure. These are practical, artifact‑level steps — they assume you can examine or query the kernel image or runtime environment.

• Identify Microsoft artifacts you run that include a Linux kernel.
• Examples: Azure Linux images, Azure Marketplace VM images, linux‑azure kernel packages used by Azure VMs, WSL2 kernel binaries distributed with Windows, container images and appliance images published by Microsoft that bundle kernels.
• For each artifact, determine the kernel version and build provenance.
• Commands: uname -r (for running systems); inspect package metadata (rpm/dpkg); check published SBOMs or the VEX/CSAF attestation (when available).
• If you cannot determine provenance, treat the artifact as potentially affected until verified.
• Check whether the bonding driver and XFRM offload code are present/enabled.
• On a running system:
• lsmod | grep bonding
• modinfo bonding
• zgrep CONFIG_BONDING /proc/config.gz (if /proc/config.gz exists)
• If bonding is present and the kernel version falls within the affected upstream commit-range, consider the artifact potentially vulnerable.
• Consult vendor/vendor‑published advisories and update channels.
• For Azure Linux, follow Microsoft’s MSRC VEX/CSAF outputs and update guidance.
• For other distributions or kernels running on Azure Marketplace images, consult the vendor or image publisher’s advisory.
• If you find vulnerable kernel artifacts, prioritize patching or rebuild:
• Apply vendor kernel updates containing the stable‑tree fixes.
• If you manage a merge upstream fixes cited in the kernel commits and rebuild with secure kernel configs.
• Use scanning and SBOM tools to locate copies of the affected kernel modules across images and containers:
• Image scanning, SBOM comparison, and binary‑artifact cataloguing will help find hidden carriers (for example, container images, appliance images, or CI/CD artifacts that embed kernel modules).

These steps are practical and repeatable; they acknowledge that Microsoft’s Azure Linux attestation helps immediately for Azure Linux customers but does not absolve operators of the need to inventory other Microsoft artifacts they run.

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Patching and mitigation — prioritized actions​

• Priority 1 — Azure Linux customers:
• Follow Microsoft’s MSRC guidance for Azure Linux and apply the published Azure Linux kernel updates as directed. Microsoft’s attestation means Azure Linux images were found to contain the implicated code and should be prioritized for patching.
• Priority 2 — Check WSL2 and linux‑azure kernels:
• Microsoft publishes WSL kernel sources and distributes WSL kernel binaries. If you run WSL2 or linux‑azure kernels (for Azure VMs or guest images), verify the kernel build and apply vendor or upstream fixes where appropriate. WSL kernels can be updated via Windows updates or by replacing the shipped kernel binary in supported scenarios — check Microsoft’s published guidance or VEX/CSAF attestations as they become available.
• Priority 3 — Marketplace images and third‑party appliances:
• Confirm whether the Marketplace image is a Microsoft‑maintained Azure Linux image (attested) or a third‑party image. If it is third‑party, consult the image publisher’s advisories and patch channels; do not assume Microsoft’s Azure Linux attestation covers it.
• Temporary mitigations if patching is delayed:
• If you cannot patch immediately and you run bonded interfaces with IPsec offload enabled, evaluate whether you can disable offload features or avoid using bonding in active scenarios until patched. That reduces the attack surface though it may not be practical in all environments.
• Monitor for kernel OOPS/panic patterns that match the vulnerability signature in your logs; treat unexplained kernel crashes during bond reconfiguration as evidence to escalate patching.

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Risk and exploitability analysis​

• Attack feasibility: the vulnerability is local (requires local or privileged access to trigger packet flows that exercise the bonding/XFRM code path) and aims at causing a kernel crash (denial of service). NVD and other trackers assign a CVSS v3.1 base score of 5.5 (Medium), with the primary impact on availability.
• Exploit complexity: low to medium. The root cause is a race; reproducing it reliably may require specific conditions (bonding mode, IPsec offload engagement, active reconfiguration of bond slaves). That said, vendors treated it as a robustness/DoS risk and issued fixes rather than waiting for broader exploit activity.
• Likely attacker benefit: denial of service only. There is no evidence this vulnerability yields arbitrary code execution or data loss beyond the typical consequences of a kernel crash (service interruption, potential file system recovery needs).
• Practical exposure: depends on how widely Microsoft products actually ship the affected bonding/XFRM code in enabled configurations. Because many Microsoft images are cloud VM kernels with different configuration choices, exposure must be determined artifact‑by‑artifact. Microsoft’s Azure Linux attestation narrows the immediate, highest‑confidence scope but does not remove the operational need to verify other artifacts.

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A pragmatic rule for defenders: treat the attestation as a starting point, not the endpoint​

Microsoft’s publication of VEX/CSAF attestations — beginning with Azure Linux — is a positive operational improvement. It gives customers a machine‑readable signal about which Microsoft product artifacts Microsoft has already inventoried. However, defenders should:

• Treat Azure Linux attestation as authoritative and actionable for Azure Linux artifacts.
• Treat other Microsoft artifacts as unverified until attested or verified locally.
• Use SBOMs, image scanning, runtime queries and vendor advisories to close the remaining gaps.

Putting it another way: the attestation answers the question “Did we find the implicated code in Azure Linux?” It does not by itself answer “Did we search every Microsoft kernel binary, WSL release, Marketplace image and appliance?” Customers must complete that latter exercise in their own environments or await expanded Microsoft attestations.

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Practical checklist for Microsoft customers and operators​

• Inventory
• Locate all images and artifacts that include Linux kernels: Azure Linux images, Marketplace VM images, containers, appliances, WSL2 kernels.
• Verify
• For each artifact, confirm kernel version and whether bonding/XFRM offload code is present (kernel configs, lsmod, modinfo).
• Patch
• Apply vendor patches or distribute rebuilt kernels that incorporate the stable‑tree fixes for CVE‑2024‑44989.
• Harden
• If patching is delayed, consider disabling bonding offload features or avoiding configurations that exercise the vulnerable path.
• Automate
• Add checks for this CVE and for the presence of bonded, offloaded IPsec state to your image‑scanning and CI pipeline.

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Final assessment and recommendations​

• Substance of the MSRC statement: correct and useful. Microsoft’s note that “Azure Linux includes this open‑source library and is therefore potentially affected” gives Azure Linux customers an immediate, actionable signal and aligns with Microsoft’s transparency program (CSAF/VEX).
• But it is not an exclusivity guarantee. Azure Linux is simply the only Microsoft product Microsoft has publicly attested to include the implicated code for this CVE so far. Other Microsoft artifacts that ship kernels — especially WSL2 kernels, linux‑azure kernels used in cloud VMs, or any bespoke kernel images — could include the same vulnerable code depending on build choices and kernel configurations. Do not assume they are safe until verified.
• Cross‑references and verification:
• The upstream kernel commit series and stable‑tree merges document the exact code changes that fixed the race. Operators and kernel packagers should prefer vendor‑supplied patches that incorporate those commits or the mainline stable tree backports.
• NVD and vendor advisories corroborate the technical details and list patched kernel releases where available. Use your vendor’s kernel advisory as the primary source for patch binaries for production systems.

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Closing thoughts​

CVE‑2024‑44989 is a classic example of how upstream kernel changes can ripple through a complex vendor ecosystem. Microsoft’s decision to begin publishing machine‑readable VEX/CSAF attestations — and to start with Azure Linux — is helpful and improves transparency for customers. But in practice, defenders must treat that attestation as one piece of an artifact‑level verification program.
If you manage Microsoft‑supplied Linux artifacts, do the inventory and verification steps listed above now: prioritize Azure Linux patches (because Microsoft has already attested it), and validate every other Microsoft image or kernel binary you run. The combination of vendor attestations, local artifact inspection, and rapid patching is the reliable path to closing exposure.

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Source: MSRC Security Update Guide - Microsoft Security Response Center