CVE-2024-27407: ntfs3 Kernel Patch to Block Local Buffer Overflow

A subtle arithmetic mistake in the Linux kernel’s NTFS3 driver has been fixed, closing CVE-2024-27407 — a locally exploitable buffer‑overflow vulnerability in the mi_enum_attr() routine that, if triggered on systems that mount NTFS volumes, can corrupt kernel memory, crash the host, and in the worst case enable privilege escalation or persistent denial of service. Security teams should treat this as a high‑impact kernel bug affecting multiple kernel series, prioritize vendor patches, and apply the mitigations described below to reduce exposure while updates are rolled out.

Background / Overview​

The Linux in‑kernel NTFS driver, ntfs3, is the kernel’s native implementation used to read and write Microsoft NTFS volumes. It is widely deployed in distributions that ship modern kernels and on systems that mount Windows-formatted disks — including many desktop, laptop, and some mixed cloud or recovery scenarios.
CVE‑2024‑27407 was published on 17 May 2024 and tracks a logic/overflow check bug in the mi_enum_attr() function inside the ntfs3 codepath. Upstream and major distributions have assigned a High severity rating to the issue (CVSS v3.1 base score 8.4 in several database listings) because the bug has a local attack vector, low complexity, and can impact confidentiality, integrity, and availability when exploited.
Administrators should note three immediate facts that determine risk and response:

• The bug is local — an attacker needs to be able to run code or deliver file operations on the targeted host (i.e., have some level of local access).
• The impact includes kernel memory corruption and system availability loss (kernel panic or persistent resource corruption), with potential privilege escalation in some exploit scenarios.
• Fixes were committed to the upstream kernel and backported by distributors; vendors published advisories and patched kernel packages. Systems should be updated to a patched kernel version as the primary mitigation.

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What went wrong inside mi_enum_attr()​

The role of mi_enum_attr()​

The mi_enum_attr() function enumerates NTFS attribute entries in on‑disk metadata structures and validates sizes and offsets as it reads attribute headers. Correct bounds checking here is crucial: a mistake can let a malformed on‑disk attribute incorrectly report a size or offset that overflows the kernel’s buffering arithmetic and causes out‑of‑bounds reads or writes. Because this code runs in kernel context while handling filesystem metadata, the consequences of a corrupted calculation are severe.

The arithmetic bug (wraparound and incorrect guard)​

Multiple vendor advisories and public vulnerability analyses explain the root cause in plain terms: the original check summed two unsigned values and compared the result to a total size, like:
if (t16 + le32_to_cpu(attr->res.data_size) > asize)
Because the addition happens before the comparison, an attacker-crafted pair of values can cause the sum to wrap around (integer overflow) and make the guard appear to pass even though the attribute's reported size does not actually fit in the remaining allocation. The correct, defensive check verifies the attribute’s size against the remaining buffer explicitly:
if (le32_to_cpu(attr->res.data_size) > asize - t16)
This change prevents arithmetic wraparound from masking an out‑of‑range attribute size. Multiple distribution security teams documented this exact fix pattern when backporting upstream mitigations.

Why that small change matters​

Unsigned integer wraparound is a common source of classic buffer overflows. When kernel code trusts on‑disk metadata without robust math and range checks, specially crafted filesystem metadata (on removable drives, disk images, or mounted partitions) can cause the kernel to read or write out of its expected memory bounds. In the kernel, such corruption frequently results in:

• immediate kernel panic (system crash, availability loss);
• memory corruption that can be weaponized into privilege escalation under specific circumstances; or
• persistent file system inconsistencies that require offline recovery and may cause prolonged service outages.

Because this code operates while enumerating attributes on NTFS volumes, any use of untrusted NTFS media or access to malformed NTFS images increases exposure.

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Scope: which kernels and platforms are affected​

Public vulnerability databases and distribution trackers show the issue affected wide ranges of kernel versions spanning multiple stable series. Different resources list overlapping version ranges — the flaw appears in numerous releases between kernel 5.15 and several 6.x series (with precise ranges varying by advisory and backport status). Distributions have produced patched kernel packages across many supported releases; users must consult their distribution’s security pages for the exact fixed package for their release.
A few practical exposure notes:

• Desktop and laptop systems that mount Windows drives (dual‑boot or external drives) are directly relevant.
• Virtual machines or containers that mount host NTFS volumes, or cloud images that include NTFS‑formatted attached storage, can be impacted.
• Systems that never mount NTFS volumes and do not load the ntfs3 module are not exposed to on‑disk attacks, but distributions that build the driver into the kernel image may still risk accidental exposure through module usage or automount behavior.

Because the kernel patch landed upstream and distributors issued fixes or backports, risk depends on whether a given box has been updated to a patched kernel package. Check your vendor advisory immediately and apply the kernel update appropriate for your distribution.

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Patches, vendor responses, and timelines​

Upstream kernel maintainers merged a small, surgical change to tighten bounds checking inside ntfs3. Distributors including Ubuntu, Debian, Amazon Linux, and others issued security updates and backports; vendor advisories and tracker pages list affected packages and fixed release versions. Canonical published an SRU and backport notes for multiple kernel trees, and AWS/ALAS and Debian’s security tracker list patched packages for their supported kernels.
When to patch:

• Prioritize production and internet‑facing systems that mount NTFS volumes or that may be given untrusted NTFS media.
• If you run kernel images provided by your vendor, install the vendor’s latest kernel update immediately.
• If you build kernels from source, pull the upstream fix and rebuild for your environment; test the new kernel in staging before rolling to production.

Acceptable short‑term compensations when immediate patching is impractical are described below, but none are as reliable as applying the vendor patch.

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Detection: signs of attempts and how to check for exploitation​

Because exploitation with NTFS metadata, look for unusual kernel messages and filesystem errors in the system logs. Administrators have reported and tool-analysts have observed messages tied to corrupt NTFS attribute records and failed attribute lookups when malformed md; these can correlate with attempted misuse of attribute enumeration. Example log lines from affected systems include messages about deleted corrupt attribute records and “Unable to locate attribute” entries — useful forensic indicators if they show up around unexpected crashes or filesystem operations.
Checkpoints for detection and triage:

• Review dmesg and /var/log/messages for NTFS3 or ntfs3 module errors, especially messages mentioning “corrupt attribute record,” “Unable to locate attribute,” or attribute instance tags that appear malformed.
• Correlate kernel oops and panic timestamps with mounts or accesses to NTFS volumes (e.g., when a removable drive was plugged in or an image was mounted).
• Search for unexplained crashes, repeated file system recovery efforts, or FSCK runs targeted at NTFS volumes after suspicious activity.
• If you have kernel crash dumps (kdump), capture and preserve them for analysis; the crash context can show if a malformed attribute header or an out‑of‑bounds pointer caused the fault.

No proof‑of‑concept exploit widely available in public exploit repositories has been reliably documented at the time of publication, but the flaw’s characteristics make it attractive for local exploitation research. Treat absence of public exploit code as a temporary reassurance — patching remains the correct defensive step.

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Recommended mitigations and short‑term workarounds​

Primary mitigation — patch the kernel:

• Apply vendor or distribution kernel updates that include the upstream fix. Distributors have published patched kernels and SRUs/backports; update strategy follows your normal change‑control and testing cycle. This is the only comprehensive fix.

Short‑term or additional mitigations while patching:

• Avoid mounting NTFS volumes from untrusted sources. Treat removable NTFS media and disk images as untrusted until you patch.
• Prefer mounting NTFS volumes read‑only when possible (mount -o ro) to reduce attack surface for code paths that write or parse attributes. Note: read‑only mounts may still trigger vulnerable code paths if the driver enumerates attributes, but risk is reduced for write-path manipulation.
• If feasible, remove or blacklist the in‑kernel ntfs3 module on systems that never need NTFS access (this may not be applicable if the module is built into the kernel rather than a loadable module). Use your distribution’s module blacklisting procedures or rebuild kernels without the module for environments where NTFS is not used.
• On systems that require NTFS access but where operational constraints allow, consider user‑space drivers (for example, ntfs‑3g via FUSE) as a temporary alternative, understanding that this may have performance and feature tradeoffs.
• Restrict unprivileged user access and tighten mount permissions to limit the ability of low‑privilege users to mount arbitrary devices or loopback images that could contain malicious NTFS metadata.

All of the above are stopgaps; the kernel update is required to fully remediate the vulnerability.

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Exploitability, threat model, and real‑world risk​

Because CVE‑2024‑27407 is a local bug, an attacker must be able to place crafted NTFS metadata on the target system or get the system to mount or access a malicious NTFS image or device. Common scenarios that increase exposure:

• Multi‑user systems where untrusted users can mount loopback images or attach devices.
• Systems that automatically mount removable devices (configurations with auto‑mount turned on).
• Hosts that process user‑supplied disk images (e.g., virtualization hosts that mount guest disk images) or ingest Windows disk images from untrusted sources.
• Laptops and desktops that frequently access external Windows drives or dual‑boot systems.

While remote, unauthenticated exploitation is not indicated by vendor advisories, the bug could be a stepping stone in multi-stage attacks where an adversary a host uses malformed NTFS metadata to escalate privileges or destabilize the system. For that reason, security teams should not treat the vulnerability as low risk simply because it’s local in nature.

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For incident responders: triage checklist​

• Preserve evidence: if a crash or suspicious event occurs, preserve /var/log, dmesg, and any kernel crash dumps (kdump vmcore).
• Identify mount history: document all mounted NTFS devices and images around the incident window.
• Correlate logs: look for NTFS attribute errors and “deleted corrupt attribute record” messages; these are strong indicators of malformed NTFS metadata interactions.
• Quarantine suspect media: isolate removable drives, loopback images, and VHD/IMG files that were accessed.
• Patch and revalidate: after applying kernel updates, re‑run the identified operations in a controlled environment to validate patch efficacy; forensic analysis can also check whether memory corruption artifacts existed prior to patching.

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Why the kernel fix is a textbook example of defensive programming​

The fix for CVE‑2024‑27407 is small but conceptually important: it changes how the code computes remaining space and validates reported attribute sizes in a way that eliminates reliance on a potentially wrapping addition. That is a standard secure‑coding pattern — compute the remaining space first, then compare the claimed size against that remaining space, rather than summing two numbers that may overflow and then comparing the result. Security engineers should treat this as a reminder that:

• Small arithmetic checks matter — simple unsigned additions are a frequent source of vulnerabilities when unchecked wraparound is possible.
• Defensive range checks prevent surprise behavior — always reason about maxima and remaining space, especially in kernel or low‑level code.
• Unit tests and fuzzing that target arithmetic boundaries are effective — fuzzers and sanitizers commonly catch these types of errors before they enter stable treeaintainers and distribution teams have proceeded to backport and package the minimal change, which is why the patch footprint is small but urgent to deploy.

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Practical checklist for sysadmins and DevOps teams​

• Inventory: identify hosts that mount NTFS volumes or have the ntfs3 driver enabled.
• Patch: apply vendor‑issued kernel packages that include the CVE‑2024‑27407 fix as a priority for affected hosts. ([alas.aws.amazon.com](CVE-2024-27407: disable automatic mounting of removable media where possible; enforce mount policies that require administrative approval.
• Monitoring: add dmesg and kernel OOPS monitoring to detection rules; alert on NTFS3‑specific error strings and repeated attribute errors.
• Testing: after patching, validate behavior by mounting known good NTFS images and running filesystem checks; for production kernels, roll patches through staging first.

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Strengths of the response and residual risks​

Strengths:

• The upstream fix is minimal and targeted, making vendor backports fast to produce and deploy. Distribution advisories and patch queues show the fix propagated across kernel trees quickly.
• Observability into failures is practical: kernel logs will generally expose malformed-attribute events, enabling incident detection for suspicious mounts.

Residual risks and caveats:

• The vulnerability is local; however, that does not imply low priority. Environments where untrusted disk images or removable media are processed remain at significant risk of privilege escalation or data destruction.
• Absence of public exploit code does not equal absence of exploitation in the wild — local, targeted attackers or red teams could weaponize the bug without public disclosure. Treat it as exploitable until proven otherwise.
• Systems that cannot be patched quickly (embedded appliances, long‑lived kernel branches, or constrained IoT devices) will need compensating controls (e.g., disallowing NTFS mounts, switching to user‑space drivers, or device isolation). These workarounds have operational tradeoffs and must be weighed carefully.

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Closon plan​

CVE‑2024‑27407 is an instructive case: a small arithmetic oversight in a filesystem driver produced a high‑severity kernel vulnerability because the driver runs with kernel privileges and processes potentially untrusted on‑disk metadata. The vulnerability illustrates how low‑level code must be written defensively against integer wraparound and how distribution security processes and upstream maintainers collaborate to produce quick, low‑risk patches.
Action items for WindowsForum readers and sysadmins right now:

• Immediately identify machines that mount NTFS volumes or host the ntfs3 driver.
• Apply vendor/kernel updates that include the CVE‑2024‑27407 fix as soon as they are available and tested for your environment.
• If patching is delayed, reduce exposure by avoiding untrusted NTFS media and mounting NTFS volumes read‑only where possible.
• Monitor kernel logs for NTFS attribute errors; preserve any crash dumps for forensic review.

Security is often won by the basics: timely patching, reducing exposure to untrusted inputs, and careful logging and monitoring. The mi_enum_attr() fix is a reminder that even tiny changes to arithmetic checks can have outsized effects on system reliability and security — and that rapid coordination between upstream maintainers and distribution security teams is essential to protect the diverse systems that run Linux today.
Conclusion: treat CVE‑2024‑27407 as a high‑priority kernel security issue for any host that processes NTFS filesystems, patch promptly, and use the monitoring and mitigation steps above to limit exposure while updates are applied.

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Source: MSRC Security Update Guide - Microsoft Security Response Center