CVE-2024-44998: Verify All Linux Kernels for the ATM idt77252 Driver

Microsoft’s CVE entry for CVE‑2024‑44998 correctly identifies a use‑after‑free bug in the Linux kernel’s ATM driver (idt77252) — but no, Azure Linux is not necessarily the only Microsoft product that can include the vulnerable code: multiple Linux kernels and Linux-based Microsoft offerings have historically carried the driver or kernel trees that include it, and vendor advisories and vulnerability trackers show the issue affecting a broad set of kernel trees (and, in published vendor mappings, multiple Microsoft-owned kernel products). The practical implication for defenders is simple: don’t assume that “only Azure Linux” is affected — verify your actual kernel package and whether the idt77252 driver is present, then patch or mitigate as appropriate.

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Background / Overview​

CVE‑2024‑44998 (published 4 September 2024; record updated 3 November 2025) describes a use‑after‑free in the ATM IDT77252 driver in the Linux kernel. The bug occurs when dequeue_rx() dereferences an sk_buff (skb) after calling vcc->push(), but the driver path can release the skb during that call — leaving the code to access freed memory. The vulnerability is classified as memory corruption (CWE‑416) and was assigned a high severity score by multiple tracking sources (CVSS v3.x values in the 7.x–7.8 range depending on the source).
The Linux kernel is an upstream open‑source project and the idt77252 driver appears in the kernel tree under drivers/atm. Because the kernel (and its drivers) are distributed as components inside many distributions and downstream kernels, a single upstream bug like this can surface in numerous vendor kernels and product images. Multiple vendor advisories (Debian, Ubuntu, Oracle, and others) and kernel changelogs record the same root cause and fixes across kernel versions.

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What the Microsoft statement says — and what it means​

Microsoft’s MSRC text quoted in the user’s prompt asks whether “Azure Linux is the only Microsoft product that includes this open‑source library and is therefore potentially affected” and highlights Microsoft’s commitment to keeping Azure Linux up to date and to publishing CSAF/VEX for transparency. That statement is an articulation of Microsoft’s public posture: they have identified Azure Linux as a product that includes the affected kernel component, and they will update the CVE product mapping if other Microsoft products are later identified as affected.
That wording is cautious and honest — it implicitly leaves open the possibility that other Microsoft Linux distributions or kernel packages may include the driver and be affected, but at the time Microsoft published that note they listed Azure Linux in their product mapping. However, independent vulnerability trackers and distribution advisories show the kernel bug mapped to multiple kernel consumers (including distributions Microsoft produces or maintains), so the conservative, operational answer for defenders is to verify rather than rely on a single vendor statement.

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Which Microsoft products could include the vulnerable code?​

Short answer: more than just the single “Azure Linux” product name may be relevant.
Why: Microsoft both maintains and distributes Linux kernels and Linux‑based images in multiple contexts:

• linux‑azure / linux‑azure packages — kernels tailored for Azure cloud VMs and used by cloud images and distribution kernels for systems running in Azure. Ubuntu’s security advisories (and other vendors’) list linux‑azure among the kernel packages that required the fix for these ATM/driver issues.
• CBL‑Mariner — Microsoft’s internal/distribution Linux used for cloud service hosts and some product images. Public vulnerability databases and vendor trackers map this kernel family to the same upstream CVEs, and CBL‑Mariner package advisories are shown as having fixes added for this CVE in timelines maintained by vulnerability databases. That indicates Microsoft’s own internal distro family can include affected kernels.
• Azure Linux (Microsoft’s branded Azure Linux offering) — explicitly called out in multiple security scanners and advisories (Nessus plugin, linux‑azure security notices, etc.) as affected and patched in various linux‑azure kernel releases.
• Other downstream kernel variants and cloud‑specific kernels — many distros maintain cloud‑tuned kernel flavors for AWS / GCP / Oracle / Azure; in upstream advisories the vulnerable code is mapped across a wide range of kernel versions, and “linux‑azure” is simply one named consumer of the kernel that included the driver.

Important nuance: Microsoft’s public CVE mapping may initially list only the product(s) they have already verified (for example, Azure Linux). That does not imply other Microsoft kernel artifacts are immune — it means Microsoft has not yet published a VEX/Csaf entry showing additional products. Independent vendor advisories (Ubuntu, Debian, CBL‑Mariner trackers, and scanning rules) show the vulnerability and fixes across multiple kernel consumers, some of which are Microsoft‑owned or Microsoft‑packaged kernels. Because of that, treating Azure Linux as the only Microsoft product that could include the driver is unsafe unless you have verified the absence of the driver or confirmed a fixed kernel is in use on each target.

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Technical summary of the bug and the code path​

• Component: drivers/atm/idt77252.c in the Linux kernel (ATM IDT77252 device driver).
• Root cause: a use‑after‑free in dequeue_rx() — code dereferences an skb after calling vcc->push(), while vcc->push() can free (release) that skb.
• Symptom: memory corruption that can lead to crash, data corruption, or other undefined behavior when a local (authenticated) user triggers the code path.
• Exploitability: local (attack requires the ability to trigger the driver path, not a typical remote vector for most cloud shells), rated high severity in vendor trackers because of the confidentiality/integrity/availability impacts of kernel memory corruption. Different repositories list CVSS values in the 7.0–7.8 range depending on scoring assumptions.

Upstream patches address the root by avoiding use‑after‑free: for example, copying or storing needed skb fields before the call that may release the skb (or otherwise avoiding dereferencing the skb after the call), and adding kernel DMA mapping error checks in related code paths. Kernel changelogs and commits show the corrective diffs.

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What you should check right now (detection and verification)​

If you manage Linux systems (including Azure VMs, managed images, or Microsoft‑provided Linux artifacts), perform the following checks immediately.

• Determine the kernel package and version
• Debian/Ubuntu: dpkg -l | grep -E 'linux-image|linux-azure|linux-.*azure'
• RPM systems: rpm -q kernel kernel-core
• Generic: uname -a
• Check the kernel version against the vulnerable ranges reported by vendors and NVD. The upstream trackers list affected ranges across many kernel releases; verify whether your running kernel falls into one of those ranges (for example, kernels in the ranges called out by NVD and distribution advisories are affected until the patched versions are applied). If you see a kernel in the vulnerable ranges, treat the system as potentially vulnerable until patched.
• Check for the presence of the idt77252 driver module or source code in the installed kernel packages
• Check loaded modules:
• lsmod | grep idt77252
• Check whether the module exists on disk:
• grep -R "idt77252" /lib/modules/$(uname -r) || ls /lib/modules/$(uname -r)/kernel/drivers/atm
• If your kernel is built with the driver statically compiled in (not a loadable module), searching /lib/modules will not find it; the presence of the driver in the kernel source tree (or in distro packaging notes) will indicate inclusion.
• You can also check package changelogs for your kernel package (apt changelog linux-image-$(uname -r) or rpm -q --changelog) for CVE‑related entries.
• Inspect logs and kernel oopses
• After the vulnerability was publicly disclosed, crashes or oopses in the ATM driver path may appear in dmesg/syslog. Search for “idt77252” or “atm” related errors in kernel logs.
• For Azure instances specifically, check the linux‑azure package and the image release notes. Ubuntu’s USNs list linux‑azure among the affected packages for kernel security updates.

If any step indicates the driver is present on a vulnerable kernel, proceed to remediation.

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Remediation and mitigation options​

Primary remediation: install the vendor/kernel update that contains the upstream fix. Distributors and kernel packagers have released fixed kernels; most major Linux vendors mapped and pushed kernel updates after the upstream fix. For systems in cloud environments, use the distro’s recommended update path and schedule a reboot as required for a kernel update. Specific actions:

• Ubuntu / Debian / linux‑azure images:
• Apply the linux‑azure or linux-image package updates recommended in the Ubuntu security notice and reboot into the patched kernel. Ubuntu’s advisories and USNs list linux‑azure as a package that received fixes in kernel updates.
• CBL‑Mariner:
• For CBL‑Mariner based images, apply the platform update that includes the fixed kernel or kernel module set; CBL‑Mariner advisories and vulnerability trackers show fixes added for kernel CVEs.
• Other distributions (Debian, Oracle Linux, SUSE, etc.):
• Follow the vendor’s kernel/security advisories and apply the appropriate kernel updates. Many vendors published fixes tied to their kernel packages.

Secondary mitigations if you cannot patch immediately (temporary, reduce exposure):

• Unload or blacklist the ATM driver (only if the driver is a loadable module and you do not need ATM functionality):
• Example:
• sudo modprobe -r idt77252 # unload module if loaded
• Create /etc/modprobe.d/blacklist-idt77252.conf containing: blacklist idt77252
• Rebuild initramfs if your distro packages the module into initramfs (update-initramfs -u or dracut --force), then reboot if necessary.
• WARNING: removing or blacklisting the driver will break any hardware or functionality that depends on ATM IDT77252. Only do this when you are sure it’s safe for your environment.
• Restrict local access:
• Because the exploit path requires local access (CVSS local vector), ensure tight controls on who can log in as local users: disable shell access for untrusted accounts and restrict sudo usage. Harden SSH access and remove unnecessary accounts.
• Audit and monitor:
• Increase monitoring for kernel oopses, suspicious local processes that might interact with kernel devices, and unexpected use of ATM device nodes. Log and escalate unusual behavior.

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Why you should not assume “only Azure Linux” matters​

• Microsoft’s public CVE mapping may be intentionally conservative — initially listing only a product they have fully verified — while downstream kernels and product images (including other Microsoft‑maintained kernels such as CBL‑Mariner or other cloud‑tuned kernel packages) may contain the same vulnerable driver in practice.
• Vulnerability trackers and distribution security notices show that the idt77252 defect was fixed in many kernel variants and distro kernels; several Linux distributions and Microsoft‑related kernel projects (linux‑azure and CBL‑Mariner) are included in those mappings in public trackers. That means the surface of “what’s affected” extends beyond a single named product in many real‑world deployments.

Operationally, the safest path is to verify the kernel package and installed modules on each host under your control (including VMs, appliances, containers that include host kernel packages, and any Microsoft‑supplied Linux images), and to apply vendor patches where the kernel is in a vulnerable range.

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Suggested prioritized checklist for administrators​

• Inventory all Linux hosts and images under your control (including Azure VMs, provider images, and Microsoft Linux artifacts such as CBL‑Mariner or linux‑azure kernels).
• On each host, run:
• uname -a
• lsmod | grep idt77252
• grep -R "idt77252" /lib/modules/$(uname -r)
• dpkg -l | grep linux-image (Debian/Ubuntu) OR rpm -qa | grep kernel (RHEL/CentOS/Oracle)
• If the module exists or kernel is in a vulnerable range:
• Plan and execute kernel updates (test patch in staging, then patch/ reboot production).
• If patching is impossible immediately, evaluate unloading/blacklisting the driver and isolate the host from untrusted local users.
• Update detection and EDR rules to look for:
• module load events for idt77252
• kernel oops/dmesg entries referencing idt77252 or atm
• Track vendor advisories and MSRC CSAF/VEX updates — Microsoft has stated it will update CVE product mappings when more impact is identified; subscribe to vendor security feeds and MSRC advisories for changes.

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Practical examples of commands to run (copy/paste friendly)​

• Identify kernel version:
• uname -r
• cat /etc/os-release
• Look for module and driver on disk:
• lsmod | grep idt77252
• grep -R --line-number idt77252 /lib/modules/$(uname -r) || true
• find /lib/modules/$(uname -r) -type f -name '*.ko' -exec modinfo {} \; 2>/dev/null | grep -i idt77252 || true
• Unload and blacklist module (if you decide it’s safe):
• sudo modprobe -r idt77252
• echo 'blacklist idt77252' | sudo tee /etc/modprobe.d/blacklist-idt77252.conf
• sudo update-initramfs -u # Debian/Ubuntu
  or sudo dracut --force # RHEL/CentOS/Oracle (if used)
• Confirm package updates:
• Debian/Ubuntu: apt update && apt list --upgradable | grep linux
• RHEL/CentOS/Oracle: yum check-update kernel

Use the vendor’s update and reboot guidance — kernel updates require a reboot to take effect.

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Risk assessment — who is most exposed?​

• Systems with the idt77252 driver present in the running kernel (built‑in or as a module) are exposed until patched or mitigated.
• The exploit vector is local, so systems that permit untrusted or multiple local users (shared VMs, developer boxes, multi‑tenant hosts without sufficient access controls) carry higher risk.
• Cloud images (Azure VM images) that use linux‑azure kernels or Microsoft‑managed kernels could be affected if their kernel build includes the driver and the kernel version is within the vulnerable ranges. Public advisories show linux‑azure was explicitly treated in vendor notices.

Note: If your environment does not use ATM hardware or the ATM driver is not present/loaded, then the practical risk on that host is low. Still, verify — presence or absence must be confirmed, not assumed.

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Final recommendations​

• Verify your kernel inventory now. Don’t rely solely on a single vendor product mapping that lists Azure Linux as the only Microsoft product affected — corroborate by checking installed kernels and modules.
• Prioritize patching of any host that runs a vulnerable kernel and contains the idt77252 driver. Apply vendor kernel updates and schedule reboots.
• If immediate patching is not possible, consider temporarily unloading or blacklisting the module when safe, and apply strict local access controls.
• Keep watch on vendor advisories (Microsoft’s MSRC CSAF/VEX feed, distro security notices) for updated product mappings; Microsoft has promised to update CVE mappings when additional affected products are identified, but you should not wait for those updates before verifying your own inventory.

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Conclusion​

CVE‑2024‑44998 is an upstream Linux kernel use‑after‑free in the ATM idt77252 driver that was fixed in upstream kernel trees and subsequently in many vendor kernel packages. Microsoft has rightly called out Azure Linux in its public messaging, but public and independent tracking shows the kernel defect appears across multiple distributions and kernel variants — including Microsoft‑maintained kernel families (linux‑azure, CBL‑Mariner variants) in real deployments. The operational imperative is straightforward: verify whether the driver is present on your systems, patch the kernel where needed, and apply short‑term mitigations for any systems that cannot be updated immediately. Don’t assume a single product name covers your entire estate — confirm, patch, and monitor.

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Source: MSRC Security Update Guide - Microsoft Security Response Center