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CVE Record

CVE-2025-40094: usb: gadget: f_acm: Refactor bind path to use __free()

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_acm: Refactor bind path to use __free() After an bind/unbind cycle, the acm->notify_req is left stale. If a subsequent bind fails, the unified error label attempts to free this stale request, leading to a NULL pointer dereference when accessing ep->ops->free_request. Refactor the error handling in the bind path to use the __free() automatic cleanup mechanism. Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020 Call trace: usb_ep_free_request+0x2c/0xec gs_free_req+0x30/0x44 acm_bind+0x1b8/0x1f4 usb_add_function+0xcc/0x1f0 configfs_composite_bind+0x468/0x588 gadget_bind_driver+0x104/0x270 really_probe+0x190/0x374 __driver_probe_device+0xa0/0x12c driver_probe_device+0x3c/0x218 __device_attach_driver+0x14c/0x188 bus_for_each_drv+0x10c/0x168 __device_attach+0xfc/0x198 device_initial_probe+0x14/0x24 bus_probe_device+0x94/0x11c device_add+0x268/0x48c usb_add_gadget+0x198/0x28c dwc3_gadget_init+0x700/0x858 __dwc3_set_mode+0x3cc/0x664 process_scheduled_works+0x1d8/0x488 worker_thread+0x244/0x334 kthread+0x114/0x1bc ret_from_fork+0x10/0x20

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in Linux’s USB gadget serial function can crash the kernel during specific device bind and unbind activity. The failure threatens system availability and may affect business operations on systems that use this functionality. General-purpose Linux systems not using USB gadget ACM likely have lower exposure.

Executive priority

Prioritize remediation on systems actively using USB gadget ACM, especially where low-privileged local users can reach the affected path. For systems without this function, confirm non-exposure and address through normal kernel maintenance. Avoid emergency claims of widespread exploitation because none are supported.

Technical view

After an ACM bind/unbind cycle, notify_req remains stale. If a later bind fails, error cleanup frees that stale request and dereferences a NULL endpoint operations pointer, causing a kernel fault. The referenced stable changes refactor bind-path cleanup using Linux’s __free() mechanism.

Likely exposure

Exposure is most likely on affected Linux versions where the USB gadget ACM function is present and exercised. Triggering requires a bind/unbind cycle followed by a failed bind. The supplied CVSS vector describes local, low-privileged access, but exact reachability depends on system configuration and permissions.

Exploitation context

The supplied record is not marked as CISA KEV, and no cited source reports active exploitation. No public exploitation evidence is established by this bundle. The demonstrated outcome is a kernel NULL pointer dereference; broader practical confidentiality or integrity impact is not explained.

Researcher notes

The source bundle provides no CWE and does not clearly map each referenced fix commit to individual stable branches. Validate branch-specific remediation with the kernel or downstream vendor. The CVSS 3.1 score is 7.8, but the narrative evidence specifically demonstrates a kernel crash rather than confirmed data compromise.

Mitigation direction

  • Apply vendor-supported kernel updates containing the applicable referenced stable fix.
  • Consult distribution or device vendor guidance to identify the correct fixed build for each maintained kernel branch.

Validation and detection

  • Inventory kernel versions and determine whether the USB gadget ACM function is present and used.
  • Compare each build with the applicable upstream stable commit and distribution or device vendor guidance.
  • Review kernel logs for faults involving usb_ep_free_request, gs_free_req, or acm_bind.
  • After updating, confirm the installed kernel contains the vendor fix and passes normal gadget bind/unbind testing.
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.

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CVE-2025-40094 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.

1CVSS vectors
3Timeline events
0ADP providers
7Source links

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
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-40094Attack 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.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1f1ba11b64947051fc32aa15fcccef6463b433f7, 1f1ba11b64947051fc32aa15fcccef6463b433f7, 1f1ba11b64947051fc32aa15fcccef6463b433f7, 1f1ba11b64947051fc32aa15fcccef6463b433f7, 1f1ba11b64947051fc32aa15fcccef6463b433f7, 1f1ba11b64947051fc32aa15fcccef6463b433f7unaffected
LinuxLinux2.6.27, 0, 5.15.196, 6.1.158, 6.6.114, 6.12.55, 6.17.5, 6.18affected
Weakness

CWE details

No CWE listed

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