Security readout for executives and security teams
Plain-English summary
CVE-2025-21642 is a Linux kernel flaw that can crash the kernel under a specific local code path involving MPTCP sysctl handling and process accounting. The business impact is availability loss, not data theft or privilege escalation, based on the supplied CVSS and description.
Executive priority
Schedule remediation in the normal kernel patch cycle, with faster handling for shared infrastructure where local users or workloads are less trusted. This is not evidenced as actively exploited, but a kernel crash can still cause service disruption.
Technical view
The MPTCP proc_scheduler sysctl path used current->nsproxy to find the network namespace. During task exit, current->nsproxy may already be dropped, causing a NULL pointer dereference and kernel oops. The CVE maps to CWE-476 and has CVSS 5.5, local, low complexity, low privileges, no user interaction, availability high.
Likely exposure
Exposure is most relevant to Linux systems running affected kernel versions or downstream kernels carrying the vulnerable MPTCP sysctl logic. The supplied record indicates local, low-privilege reachability and does not show remote network exploitation.
Exploitation context
The source cites syzbot finding the issue through acct(2) during task exit. CISA KEV status is false in the bundle, and no cited source states active exploitation. Treat it as a local denial-of-service risk until vendor guidance says otherwise.
Researcher notes
Key behavior is namespace lookup through current->nsproxy instead of table-associated per-netns data. The supplied evidence supports NULL pointer dereference and availability impact only. Affected-version data in the bundle is limited and should be reconciled against upstream commits and distribution backports.
Mitigation direction
- Apply vendor kernel updates that include the referenced stable Linux fixes.
- Prioritize multi-user, shared, and container-host Linux systems first.
- Check distribution advisories for exact affected package versions and backports.
- Avoid direct wrangler-style assumptions: verify downstream kernel patch status, not only upstream version numbers.
Validation and detection
- Inventory Linux kernel versions across servers and appliances.
- Check whether kernels include the referenced stable commits or vendor backports.
- Identify systems where local users or workloads can reach relevant sysctl/accounting paths.
- Confirm monitoring alerts for kernel oops, panic, or unexpected reboot events.
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-476: 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-2025-21642 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/c0e394fd6b887e84da17e38aaa6c1c104f9c86c2CVE reference, Linux
- https://git.kernel.org/stable/c/6035702381c35a8f16757332381e58b348a9eaf9CVE reference, Linux
- https://git.kernel.org/stable/c/d38e26e36206ae3d544d496513212ae931d1da0aCVE 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.
NULL Pointer Dereference
NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.