Security readout for executives and security teams
Plain-English summary
CVE-2025-21851 is a low-severity Linux kernel availability issue. On aarch64 systems built with 64KB pages, specific BPF arena cleanup behavior can trigger a segmentation fault and soft lockup. It requires local low-privilege access and does not indicate data theft or privilege escalation.
Executive priority
Handle through normal kernel patch governance, with priority for aarch64 64KB-page fleets. This is not presented as internet-exploitable or actively exploited, but it can affect system availability where local users or workloads can reach the vulnerable path.
Technical view
The bug is in Linux BPF arena map cleanup. arena_map_free() passed a potentially unaligned address into apply_to_existing_page_range(), which could reach apply_to_pte_range() unaligned and cause soft lockup on CONFIG_PAGE_SIZE_64KB aarch64 kernels. The fix aligns GUARD_SZ so bpf_arena_get_kern_vm_start() returns a page-aligned value.
Likely exposure
Exposure appears limited to Linux systems with affected kernel versions and aarch64 64KB page builds where BPF arena functionality is reachable by a local user. Standard x86 deployments and aarch64 4KB page builds are not described as affected in the provided sources.
Exploitation context
The CVSS vector is local, low complexity, low privileges, no user interaction, and availability-only impact. The source bundle does not cite public exploitation, and KEV is false. Treat this as a targeted local denial-of-service risk unless vendor advisories say otherwise.
Researcher notes
The available evidence is authoritative but narrow: CVE metadata and kernel stable fixes. It does not provide distribution package mappings, proof-of-concept status, or exploitation reports. Avoid broad exposure claims beyond local availability impact on the described Linux kernel configuration.
Mitigation direction
- Apply Linux vendor or stable kernel updates containing the referenced fixes.
- Prioritize aarch64 systems built with CONFIG_PAGE_SIZE_64KB.
- Check distribution advisories for exact package names and backport status.
- If patching is delayed, review vendor guidance for BPF exposure controls.
Validation and detection
- Inventory Linux kernel versions and architecture across managed hosts.
- Confirm whether affected aarch64 hosts use CONFIG_PAGE_SIZE_64KB.
- Verify updated kernels include the referenced stable commits or vendor backports.
- Review kernel logs for soft lockups involving BPF arena cleanup.
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-667: Exact CWE lookup
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Open ATT&CK lookupCVE-2025-21851 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
- Low
- CVSS
- 3.3 (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:L
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:L1.81.4CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
3.3LowVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
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/c1f3f3892d4526f18aaeffdb6068ce861e793ee3CVE reference, Linux
- https://git.kernel.org/stable/c/787d556a3de447e70964a4bdeba9196f62a62b1eCVE reference, Linux
- https://git.kernel.org/stable/c/517e8a7835e8cfb398a0aeb0133de50e31cae32bCVE 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.
Improper Locking
Improper Locking represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.