Security readout for executives and security teams
Plain-English summary
CVE-2025-39800 is a Linux Btrfs flaw that can allow filesystem metadata with an unexpected generation value to be committed instead of safely rejecting it. The supplied CVSS score is 7.8, reflecting potentially serious confidentiality, integrity, and availability consequences. Exploitation requires local access with low privileges; the available evidence does not establish practical exploitability.
Executive priority
Treat this as a high-priority kernel maintenance issue on Btrfs systems, especially multi-user hosts or products permitting local untrusted access. It is not supported as an emergency internet-wide threat because the vector is local and no active exploitation is documented. Expedite normal patching after confirming vendor applicability and test filesystem-dependent workloads before broad rollout.
Technical view
During btrfs_copy_root(), an unexpected extent-buffer generation previously caused only WARN_ON(), allowing suspect metadata to persist. The correction aborts the transaction and returns -EUCLEAN. The supplied CVSS vector is local, low complexity, low privileges, no user interaction, unchanged scope, with high confidentiality, integrity, and availability impacts.
Likely exposure
Exposure is limited to systems running affected Linux kernels where Btrfs is present and the vulnerable btrfs_copy_root() path can be reached. The bundle lists affected releases beginning with 2.6.29 and several later kernel lines, but does not provide complete distribution package mappings. Confirm status through the applicable Linux distributor or product vendor.
Exploitation context
CISA KEV status is false, and the supplied sources do not report active exploitation or a public exploit. The CVSS vector indicates a local attacker with low privileges, not a remote unauthenticated attacker. The evidence does not explain how an attacker could reliably create the unexpected generation condition, so real-world exploitability remains uncertain.
Researcher notes
No CWE is supplied. The documented unsafe behavior is persistence of metadata carrying an unexpected extent-buffer generation; the fix converts a warning into transaction abortion with -EUCLEAN. The bundle provides several stable-kernel commits but no complete vulnerable-range derivation, trigger details, proof of concept, forensic signature, or evidence connecting the condition to demonstrated confidentiality, integrity, and availability compromise.
Mitigation direction
- Install a vendor-supported kernel update containing the applicable stable fix.
- Follow distribution or appliance vendor guidance for exact fixed package versions.
- Prioritize Btrfs systems accessible to untrusted or low-privileged local users.
- Restrict unnecessary local access until affected systems are updated.
Validation and detection
- Inventory kernel versions and identify systems actively using Btrfs filesystems.
- Compare installed kernel packages with current distributor or product-vendor advisories.
- Confirm the deployed kernel includes the applicable referenced stable fix.
- Review kernel logs for relevant Btrfs warnings, without treating their absence as proof of safety.
- Recheck kernel and Btrfs status after rebooting into the updated kernel.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2025-39800 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9LinuxVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/4290e34fb87ae556b12c216efd0ae91583446b7aCVE reference, Linux
- https://git.kernel.org/stable/c/4734255ef39b416864139dcda96a387fe5f33a6aCVE reference, Linux
- https://git.kernel.org/stable/c/da2124719f386b6e5d4d4b1a2e67c440e4d5892fCVE reference, Linux
- https://git.kernel.org/stable/c/f4f5bd9251a4cbe55aaa05725c6c3c32ad1f74b3CVE reference, Linux
- https://git.kernel.org/stable/c/33e8f24b52d2796b8cfb28c19a1a7dd6476323a8CVE reference, Linux
- https://lists.debian.org/debian-lts-announce/2025/10/msg00008.htmlCVE reference, CVE
- https://cert-portal.siemens.com/productcert/html/ssa-032379.htmlCVE reference, siemens-SADP
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.