Vulnerability Database

374,588

Total vulnerabilities in the database

CVE-2023-53618 — linux / linux_kernel

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

btrfs: reject invalid reloc tree root keys with stack dump

[BUG] Syzbot reported a crash that an ASSERT() got triggered inside prepare_to_merge().

That ASSERT() makes sure the reloc tree is properly pointed back by its subvolume tree.

[CAUSE] After more debugging output, it turns out we had an invalid reloc tree:

BTRFS error (device loop1): reloc tree mismatch, root 8 has no reloc root, expect reloc root key (-8, 132, 8) gen 17

Note the above root key is (TREE_RELOC_OBJECTID, ROOT_ITEM, QUOTA_TREE_OBJECTID), meaning it's a reloc tree for quota tree.

But reloc trees can only exist for subvolumes, as for non-subvolume trees, we just COW the involved tree block, no need to create a reloc tree since those tree blocks won't be shared with other trees.

Only subvolumes tree can share tree blocks with other trees (thus they have BTRFS_ROOT_SHAREABLE flag).

Thus this new debug output proves my previous assumption that corrupted on-disk data can trigger that ASSERT().

[FIX] Besides the dedicated fix and the graceful exit, also let tree-checker to check such root keys, to make sure reloc trees can only exist for subvolumes.

  • Published: Oct 7, 2025
  • Updated: Feb 6, 2026
  • CVE: CVE-2023-53618
  • Severity: Medium
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: Medium
  • Score: 5.5
  • AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

No CWE or OWASP classifications available.

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.