Security readout for executives and security teams
Plain-English summary
This Linux kernel issue can let a local authenticated user trigger a serious availability problem through a CIFS mount option. It is not a remote internet-facing bug by itself. Business urgency is highest for multi-user Linux servers, shared hosting, build hosts, or systems where untrusted users can perform CIFS mounts.
Executive priority
Treat as a routine but real availability patching item. Prioritize shared Linux infrastructure and systems with local user access before single-purpose servers with tightly controlled administration.
Technical view
CVE-2025-21964 is an integer overflow in Linux CIFS handling of the user-supplied acregmax mount option. The value is converted from seconds to jiffies before validation, allowing overflow. CVSS 3.1 is 5.5 with local access, low complexity, low privileges, no user interaction, and high availability impact.
Likely exposure
Likely exposed assets are Linux systems using the CIFS client where low-privileged local users can invoke or influence CIFS mounts. Exposure is lower on single-user systems or hosts where CIFS mounting is unavailable or restricted to administrators.
Exploitation context
The source bundle does not show known active exploitation, and KEV status is false. The issue requires local low-privileged access, so it is more relevant for privilege-separated shared systems than for perimeter-only risk.
Researcher notes
Focus validation on CIFS mount option parsing and vendor backport status. The provided evidence identifies CWE-190 and upstream stable commits, but does not provide exploit details or distribution-specific fixed versions beyond the referenced advisories.
Mitigation direction
- Apply Linux stable or distribution kernel updates that include the cited CIFS fix.
- Check vendor advisories for exact fixed package versions for each distribution.
- Restrict CIFS mount capability to trusted administrators where operationally feasible.
- Review systems allowing untrusted local users or automated mount requests.
Validation and detection
- Inventory Linux kernel versions and compare them with vendor CVE-2025-21964 guidance.
- Identify hosts where CIFS mounts are enabled or routinely used.
- Verify whether low-privileged users can perform CIFS mounts.
- Confirm patched kernels include one of the cited upstream stable fixes.
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-190: 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-2025-21964 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
- Medium
- CVSS
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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
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:N/I:N/A:H1.83.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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/a13351624a6af8d91398860b8c9d4cf6c8e63de5CVE reference, Linux
- https://git.kernel.org/stable/c/dd190168e60ac15408f074a1fe0ce36aff34027bCVE reference, Linux
- https://git.kernel.org/stable/c/0252c33cc943e9e48ddfafaa6b1eb72adb68a099CVE reference, Linux
- https://git.kernel.org/stable/c/833f2903eb8b70faca7967319e580e9ce69729fcCVE reference, Linux
- https://git.kernel.org/stable/c/5f500874ab9b3cc8c169c2ab49f00b838520b9c5CVE reference, Linux
- https://git.kernel.org/stable/c/7489161b1852390b4413d57f2457cd40b34da6ccCVE reference, Linux
- https://lists.debian.org/debian-lts-announce/2025/05/msg00045.htmlCVE reference, CVE
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.
Integer Overflow or Wraparound
Integer Overflow or Wraparound represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.