Security readout for executives and security teams
Plain-English summary
A flaw in the Linux kernel’s FUSE handling can write beyond allocated memory when processing a specially shaped local operation. Successful exploitation could compromise confidentiality, integrity, and availability. The supplied evidence indicates local, low-privilege access is required; it does not establish remote or active exploitation.
Executive priority
Treat this as a high-priority kernel update for exposed multi-user or untrusted-workload systems. It is not evidenced as an internet-scale emergency, but potential full confidentiality, integrity, and availability impact warrants prompt remediation through normal emergency patch governance.
Technical view
CVE-2025-39888 is a CWE-787 slab out-of-bounds write in fuse_dev_do_write. It occurs when retrieval length is capped by fc->max_pages while a nonzero offset remains, allowing iteration beyond the folio limit. The kernel fix adds a loop termination condition preventing the overrun.
Likely exposure
Exposure is limited to Linux systems running affected kernel builds where a local low-privileged actor can reach the vulnerable FUSE path. The bundle names 6.16, 6.16.8, and 6.17, but its version representation is ambiguous; confirm exact affected ranges with the distribution or kernel vendor.
Exploitation context
The CVSS vector rates exploitation as local, low complexity, low privilege, and requiring no user interaction, with potentially high impact. CISA KEV status is false, and the supplied sources provide no evidence of exploitation in the wild or a public exploit.
Researcher notes
The source describes a syzkaller-reported slab out-of-bounds write and a bounded-loop correction. Exact affected and fixed release boundaries are not clearly encoded in the supplied bundle. No exploitability analysis beyond CVSS, proof of exploitation, attack payload, or distribution-specific package mapping is provided.
Mitigation direction
- Apply a vendor kernel update containing the referenced upstream correction.
- Consult distribution guidance to identify fixed package versions; do not rely solely on the ambiguous version metadata.
- Prioritize multi-user systems and workloads permitting untrusted local access to FUSE functionality.
- Use vendor-supported exposure reduction guidance if immediate kernel updating is unavailable.
Validation and detection
- Inventory running kernel versions and compare them with current distribution advisories.
- Confirm the installed kernel source or package includes one of the referenced stable corrections.
- Identify systems allowing untrusted local users or FUSE-dependent workloads.
- After updating, reboot into the corrected kernel and verify the active version.
- Regression-test legitimate FUSE mounts and applications after remediation.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-787: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2025-39888 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.
SSVC decision data
CVSS vector scores
2 official scoresWe 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:H1.85.9LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9CISA-ADPVulnerability 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
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/623719227b114d73a2cee45f1b343ced63ce09ecCVE reference, Linux
- https://git.kernel.org/stable/c/9d81ba6d49a7457784f0b6a71046818b86ec7e44CVE reference, Linux
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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.