Security readout for executives and security teams
Plain-English summary
A local user who can access a specially configured Linux tracing buffer may trigger a kernel fault by mapping it into memory. The documented result is a system crash, creating a denial-of-service risk. Although the CVSS assessment allows broader confidentiality and integrity impact, the supplied evidence demonstrates a crash only.
Executive priority
Prioritize affected multi-user, administrative, development, and observability systems where local users can reach tracing interfaces. Patch through normal expedited kernel maintenance. Urgency is lower where reserve_mem persistent tracing is absent or inaccessible, but configuration should be verified rather than assumed.
Technical view
Persistent tracing ring buffers backed by reserve_mem use vmap-managed memory. The mmap path incorrectly passes addresses through virt_to_page() before vm_insert_pages(), which can cause a kernel page fault. The Linux fix rejects mmap requests for these persistent buffers with -ENODEV.
Likely exposure
Exposure requires an affected Linux kernel, a tracing instance using a reserve_mem-backed persistent ring buffer, and local access to the relevant mmap interface. The source lists 6.12, 6.12.16, 6.13.4, and 6.14 as affected; its separate “0” version entry is ambiguous.
Exploitation context
The CVSS vector describes local, low-complexity exploitation requiring low privileges and no user interaction. The supplied record is not in KEV and provides no evidence of active exploitation. It documents a reproducible kernel crash, but does not establish practical confidentiality or integrity compromise.
Researcher notes
The demonstrated failure occurs when virt_to_page() handles vmap-backed persistent ring-buffer memory. The chosen remediation disables this mmap combination instead of adding mapping support. The source does not identify a CWE, public exploit, affected distribution packages, or proof of impact beyond the kernel fault. Version applicability should be confirmed against stable commits and distributor backports.
Mitigation direction
- Update to a vendor-supported kernel containing the applicable cited stable fix.
- Until updated, avoid reserve_mem-backed persistent tracing buffers where operationally feasible.
- Restrict local access to tracing interfaces according to vendor and platform guidance.
- Review Linux distribution advisories for exact fixed package versions.
Validation and detection
- Inventory kernel versions across hosts and compare them with vendor advisories.
- Identify systems using tracing instances backed by the reserve_mem option.
- Confirm the installed kernel includes the applicable stable fix commit.
- In authorized non-production testing, confirm persistent-buffer mmap requests return -ENODEV.
- Monitor kernel logs for page faults involving tracing_buffers_mmap or ring_buffer_map.
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
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ATT&CK lookup starting points
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CVE-2025-21778 mapping review
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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.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/e8dff5f73912513fc9b52ab992d861517c9a9975CVE reference, Linux
- https://git.kernel.org/stable/c/cf5aa560e5c7628b57c928741d7e6a9a0f6f0e67CVE reference, Linux
- https://git.kernel.org/stable/c/129fe718819cc5e24ea2f489db9ccd4371f0c6f6CVE 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.