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CVE-2026-93800

Vulnerability in Linux kernel (CVE-2026-93800)

Summary

Vulnerability in Linux kernel (CVE-2026-93800). Risk of unauthorized operations or information disclosure.

Original description

The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved:

btrfs: fix use-after-free on reloc root after error in insert_dirty_subvol()

If during relocation we fail in insert_dirty_subvol() because
btrfs_update_reloc_root() returned an error, we will leave a root's
reloc_root field pointing to a reloc root that was freed instead of NULL,
resulting later in a use-after-free, or double free attempt during
unmount.

The sequence of steps is this:

  1. During relocation the call to btrfs_update_reloc_root() in
    insert_dirty_subvol() fails, so insert_dirty_subvol() returns the
    error to merge_reloc_root() without adding the root to the list
    rc->dirty_subvol_roots;

  2. Then merge_reloc_root() aborts the current transaction because
    insert_dirty_subvol() returned an error;

  3. Up the call chain, merge_reloc_roots() gets the error, adds the
    reloc root for root X to the local reloc_roots list and jumps to the
    'out' label, where it calls free_reloc_roots() to free all the reloc
    roots in the local reloc_roots list. This frees the reloc root for
    root X;

  4. We go up the call chain to relocate_block_group() which calls
    clean_dirty_subvols() to go over dirty roots and set their
    ->reloc_root field to NULL, but root X is not in the dirty_subvol_roots
    list, so its ->reloc_root still points to a reloc root;

  5. Relocation finishes, with an error and a transaction abort, but the
    ->reloc_root field for root X still points to the reloc root that was
    f…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-93800 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-93800" on the vendor's site.

CVE-2026-93800 (Linux kernel)
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in Linux kernel.

📍 Affected scope

Check the vendor advisory for the affected versions of Linux kernel.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

References

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