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CVE Record

CVE-2025-21669: vsock/virtio: discard packets if the transport changes

In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: discard packets if the transport changes If the socket has been de-assigned or assigned to another transport, we must discard any packets received because they are not expected and would cause issues when we access vsk->transport. A possible scenario is described by Hyunwoo Kim in the attached link, where after a first connect() interrupted by a signal, and a second connect() failed, we can find `vsk->transport` at NULL, leading to a NULL pointer dereference.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A local, low-privileged user may trigger unsafe Linux virtio-vsock handling after a connection is interrupted and another connection fails. The kernel can then access a missing transport object and crash. The supplied CVSS score is 7.8, but the source narrative specifically demonstrates a NULL pointer dereference rather than confirmed data theft or privilege escalation.

Executive priority

Treat this as a high-priority kernel patching item for exposed virtualization environments, but not as an internet-scale emergency. Focus first on multi-user or shared systems using virtio-vsock. Accelerate response if local accounts are untrusted or kernel crashes would materially disrupt critical services.

Technical view

CVE-2025-21669 is a CWE-476 flaw in Linux virtio-vsock. Packets were not discarded after a socket transport was removed or changed. A signal-interrupted connect, followed by a failed connect and unexpected packet, can leave vsk->transport NULL and cause a kernel NULL pointer dereference. Stable-kernel commits add transport-change packet rejection.

Likely exposure

Exposure is most relevant to Linux systems using virtio-vsock where a low-privileged local user can exercise socket connections. The supplied affected-version data begins at 5.5 but ambiguously mixes version and fix information. Distribution kernels may contain backports, so package version alone is insufficient.

Exploitation context

The supplied CVSS vector requires local access, low privileges, low complexity, and no user interaction. The described trigger involves particular connection failures and packet timing. CISA KEV status is false, and the supplied sources provide no evidence of active exploitation. Public proof-of-concept availability is not established by this bundle.

Researcher notes

The bundle repeats one commit identifier and presents affected versions without explicit range semantics, limiting precise upstream version conclusions. Confirm exposure against the exact distribution build and backport history. The CVSS vector rates confidentiality, integrity, and availability impacts high, while the supplied technical description directly substantiates only a NULL pointer dereference.

Mitigation direction

  • Install a vendor-supported kernel update containing the applicable Linux stable fix.
  • Check distribution and appliance advisories because vendors may backport the patch without changing upstream version numbering.
  • Prioritize shared virtualization hosts and workloads that actively use virtio-vsock.
  • If immediate updating is impossible, assess whether virtio-vsock can be safely disabled according to vendor guidance.

Validation and detection

  • Inventory active kernel builds and identify systems using virtio-vsock.
  • Map each kernel build to its vendor advisory, backport record, or applicable stable commit.
  • After updating, confirm the patched kernel is active following the required reboot.
  • Review kernel logs for NULL pointer dereferences involving vsock or virtio transport handling.
Prepared
Confidence
medium
Sources
8

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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cwe · low confidence lookup

CWE-476: Exact CWE lookup

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cve · low confidence lookup

CVE-2025-21669 mapping review

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Vulnerability profileCVE Program record
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

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.

2CVSS vectors
3Timeline events
3ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We 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.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux
5.5CVSS 3.1MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-21669Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container
siemens-SADPADP container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxc0cfa2d8a788fcf45df5bf4070ab2474c88d543a, c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, c0cfa2d8a788fcf45df5bf4070ab2474c88d543a, c0cfa2d8a788fcf45df5bf4070ab2474c88d543aunaffected
LinuxLinux5.5, 0, 5.10.234, 5.15.177, 6.1.127, 6.6.74, 6.12.11, 6.13affected
Weakness

CWE details

CWE-476

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

CWE-476 · source CWE mapping

NULL Pointer Dereference

NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs