LiveActive security incident?Get immediate response
CVE Record

CVE-2025-21854: sockmap, vsock: For connectible sockets allow only connected

In the Linux kernel, the following vulnerability has been resolved: sockmap, vsock: For connectible sockets allow only connected sockmap expects all vsocks to have a transport assigned, which is expressed in vsock_proto::psock_update_sk_prot(). However, there is an edge case where an unconnected (connectible) socket may lose its previously assigned transport. This is handled with a NULL check in the vsock/BPF recv path. Another design detail is that listening vsocks are not supposed to have any transport assigned at all. Which implies they are not supported by the sockmap. But this is complicated by the fact that a socket, before switching to TCP_LISTEN, may have had some transport assigned during a failed connect() attempt. Hence, we may end up with a listening vsock in a sockmap, which blows up quickly: KASAN: null-ptr-deref in range [0x0000000000000120-0x0000000000000127] CPU: 7 UID: 0 PID: 56 Comm: kworker/7:0 Not tainted 6.14.0-rc1+ Workqueue: vsock-loopback vsock_loopback_work RIP: 0010:vsock_read_skb+0x4b/0x90 Call Trace: sk_psock_verdict_data_ready+0xa4/0x2e0 virtio_transport_recv_pkt+0x1ca8/0x2acc vsock_loopback_work+0x27d/0x3f0 process_one_work+0x846/0x1420 worker_thread+0x5b3/0xf80 kthread+0x35a/0x700 ret_from_fork+0x2d/0x70 ret_from_fork_asm+0x1a/0x30 For connectible sockets, instead of relying solely on the state of vsk->transport, tell sockmap to only allow those representing established connections. This aligns with the behaviour for AF_INET and AF_UNIX.

MediumCVSS 5.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel crash bug, not a data theft issue. A local low-privileged user could trigger a null pointer dereference in a vsock/sockmap edge case, causing denial of service. The sources do not show remote exploitation or active exploitation.

Executive priority

Treat as a normal-priority kernel availability fix unless the environment has many untrusted local users or tenants. It is not evidenced as internet-exploitable, but kernel crashes can still disrupt business services.

Technical view

CVE-2025-21854 is a CWE-476 null pointer dereference in Linux sockmap handling for connectible vsock sockets. Listening or unconnected vsocks could enter sockmap with invalid transport state, leading to a KASAN null-ptr-deref in vsock_read_skb. The fix restricts connectible sockets to established connections.

Likely exposure

Exposure is mainly Linux hosts running affected kernels where local users or workloads can interact with vsock and BPF sockmap paths. The CVSS vector is local, low complexity, low privileges, no user interaction, and high availability impact.

Exploitation context

The CVE record marks KEV as false, and the supplied sources do not report active exploitation. The impact is availability-only in the provided CVSS data, with no stated confidentiality or integrity impact.

Researcher notes

Key condition is a connectible vsock entering sockmap without the established connection state sockmap expects. The patch aligns behavior with AF_INET and AF_UNIX by allowing only established connectible sockets. Affected-version details in the bundle are limited and should be reconciled with distro backports.

Mitigation direction

  • Apply Linux kernel updates containing the referenced stable fixes or vendor backports.
  • Prioritize multi-user systems, virtualization hosts, and container platforms with untrusted local workloads.
  • Check distribution advisories before assuming exact affected package versions.
  • Reduce unnecessary access to BPF or vsock features where operationally feasible.

Validation and detection

  • Inventory Linux kernel versions across affected server and workstation fleets.
  • Confirm vendor kernel packages include a fix for CVE-2025-21854.
  • Review whether hosts expose vsock and BPF sockmap usage to untrusted local users.
  • Track remediation through reboot completion, not package installation alone.
Prepared
Confidence
high
Sources
6

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

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

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 lookup
cve · low confidence lookup

CVE-2025-21854 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
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

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.

1CVSS vectors
3Timeline events
1ADP providers
5Source links

SSVC decision data

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

CVSS vector scores

1 official score

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
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

5.5Medium
CVSS 3.1 vector shape for CVE-2025-21854Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux634f1a7110b439c65fd8a809171c1d2d28bcea6f, 634f1a7110b439c65fd8a809171c1d2d28bcea6f, 634f1a7110b439c65fd8a809171c1d2d28bcea6f, 634f1a7110b439c65fd8a809171c1d2d28bcea6funaffected
LinuxLinux6.4, 0, 6.6.80, 6.12.17, 6.13.5, 6.14affected
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