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CVE Record

CVE-2025-21903: mctp i3c: handle NULL header address

In the Linux kernel, the following vulnerability has been resolved: mctp i3c: handle NULL header address daddr can be NULL if there is no neighbour table entry present, in that case the tx packet should be dropped. saddr will usually be set by MCTP core, but check for NULL in case a packet is transmitted by a different protocol.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2025-21903 is a Linux kernel issue in the MCTP over I3C transmit path. The fix handles missing source or destination header addresses by dropping the packet instead of processing invalid state. Public sources do not provide CVSS, CWE, or a confirmed business impact.

Executive priority

Treat as a routine-to-prioritized kernel maintenance item unless your environment uses MCTP over I3C. Lack of severity scoring and exploitation evidence lowers urgency, but kernel defects should still be addressed through normal patch cycles.

Technical view

The Linux kernel MCTP I3C code could encounter NULL destination or source address pointers during transmit. The upstream resolution adds checks for NULL header addresses and drops affected packets. The CVE record lists Linux kernel versions as affected, but the provided version data is not fully explanatory.

Likely exposure

Exposure appears limited to Linux systems using or enabling MCTP over I3C functionality. Systems without this kernel feature, hardware path, or protocol use are less likely exposed. Confirm through kernel configuration and vendor advisories.

Exploitation context

No CISA KEV listing or cited source indicates active exploitation. The public sources describe a kernel fix, not exploitability, attack prerequisites, or demonstrated impact.

Researcher notes

Evidence is sparse. The sources identify the fix behavior but not root-cause impact, privilege requirements, reachability, or affected configuration details. Avoid assuming remote exploitability or active abuse without additional vendor analysis.

Mitigation direction

  • Apply a Linux kernel update that includes the referenced stable fixes.
  • Check Linux distribution advisories for packaged fixed versions.
  • Prioritize systems using MCTP over I3C or related platform-management hardware paths.
  • If patching is delayed, consult vendor guidance for supported risk reduction.

Validation and detection

  • Inventory Linux kernel versions across affected assets.
  • Determine whether MCTP over I3C support is enabled or in use.
  • Verify installed kernel packages include one of the referenced stable commits.
  • Track distribution security advisories for CVE-2025-21903 status.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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

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CVE-2025-21903 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

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.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxc8755b29b58ec65be17bcb8c40763d2dcb1f1db5, c8755b29b58ec65be17bcb8c40763d2dcb1f1db5, c8755b29b58ec65be17bcb8c40763d2dcb1f1db5unaffected
LinuxLinux6.7, 0, 6.12.19, 6.13.7, 6.14affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.