# CVE-2026-43187: xfs: delete attr leaf freemap entries when empty > An integer underflow in the XFS filesystem can cause data loss by allowing extended attribute entries to overwrite existing data. - **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 6 May 2026 - **Updated:** 19 Oct 2026 - **Also known as:** BELL-CVE-2026-43187, DEBIAN-CVE-2026-43187, GHSA-8h5h-g93f-3ff6, ROOT-OS-DEBIAN-11-CVE-2026-43187, ROOT-OS-UBUNTU-2204-CVE-2026-43187, ROOT-OS-UBUNTU-2404-CVE-2026-43187, UBUNTU-CVE-2026-43187 ## What is CVE-2026-43187? CVE-2026-43187 is a high-severity vulnerability in Linux kernel, published on 6 May 2026. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description In the Linux kernel, the following vulnerability has been resolved: xfs: delete attr leaf freemap entries when empty Back in commit 2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow"), Brian Foster observed that it's possible for a small freemap at the end of the end of the xattr entries array to experience a size underflow when subtracting the space consumed by an expansion of the entries array. There are only three freemap entries, which means that it is not a complete index of all free space in the leaf block. This code can leave behind a zero-length freemap entry with a nonzero base. Subsequent setxattr operations can increase the base up to the point that it overlaps with another freemap entry. This isn't in and of itself a problem because the code in _leaf_add that finds free space ignores any freemap entry with zero size. However, there's another bug in the freemap update code in _leaf_add, which is that it fails to update a freemap entry that begins midway through the xattr entry that was just appended to the array. That can result in the freemap containing two entries with the same base but different sizes (0 for the "pushed-up" entry, nonzero for the entry that's actually tracking free space). A subsequent _leaf_add can then allocate xattr namevalue entries on top of the entries array, leading to data loss. But fixing that is for later. For now, eliminate the possibility of confusion by zeroing out the base of any freemap entry that has zero size. Because the freemap is not intended to be a complete index of free space, a subsequent failure to find any free space for a new xattr will trigger block compaction, which regenerates the freemap. It looks like this bug has been in the codebase for quite a long time. Weakness: CWE-191 (Integer Underflow (Wrap or Wraparound)), CWE-190 (Integer Overflow or Wraparound) ## Which versions are affected by CVE-2026-43187? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2026-43187? Apply the vendor's patch. ## Is CVE-2026-43187 being exploited? There is no known exploitation of CVE-2026-43187 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-43187 and fix it if it is affected. What it is: CVE-2026-43187 is a high-severity vulnerability in Linux kernel, published on 6 May 2026. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-43187 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-43187/ (Markdown: https://insights.sbomify.com/CVE-2026-43187/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43187 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43187 - OSV: https://osv.dev/vulnerability/CVE-2026-43187 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-43187/ Summaries are generated and may contain mistakes; the official description above is the record.