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CVE Record

CVE-2024-26996: usb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: Fix UAF ncm object at re-bind after usb ep transport error When ncm function is working and then stop usb0 interface for link down, eth_stop() is called. At this piont, accidentally if usb transport error should happen in usb_ep_enable(), 'in_ep' and/or 'out_ep' may not be enabled. After that, ncm_disable() is called to disable for ncm unbind but gether_disconnect() is never called since 'in_ep' is not enabled. As the result, ncm object is released in ncm unbind but 'dev->port_usb' associated to 'ncm->port' is not NULL. And when ncm bind again to recover netdev, ncm object is reallocated but usb0 interface is already associated to previous released ncm object. Therefore, once usb0 interface is up and eth_start_xmit() is called, released ncm object is dereferrenced and it might cause use-after-free memory. [function unlink via configfs] usb0: eth_stop dev->port_usb=ffffff9b179c3200 --> error happens in usb_ep_enable(). NCM: ncm_disable: ncm=ffffff9b179c3200 --> no gether_disconnect() since ncm->port.in_ep->enabled is false. NCM: ncm_unbind: ncm unbind ncm=ffffff9b179c3200 NCM: ncm_free: ncm free ncm=ffffff9b179c3200 <-- released ncm [function link via configfs] NCM: ncm_alloc: ncm alloc ncm=ffffff9ac4f8a000 NCM: ncm_bind: ncm bind ncm=ffffff9ac4f8a000 NCM: ncm_set_alt: ncm=ffffff9ac4f8a000 alt=0 usb0: eth_open dev->port_usb=ffffff9b179c3200 <-- previous released ncm usb0: eth_start dev->port_usb=ffffff9b179c3200 <-- eth_start_xmit() --> dev->wrap() Unable to handle kernel paging request at virtual address dead00000000014f This patch addresses the issue by checking if 'ncm->netdev' is not NULL at ncm_disable() to call gether_disconnect() to deassociate 'dev->port_usb'. It's more reasonable to check 'ncm->netdev' to call gether_connect/disconnect rather than check 'ncm->port.in_ep->enabled' since it might not be enabled but the gether connection might be established.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A Linux USB networking flaw can leave the kernel using an object after it has been freed. Under a specific USB NCM failure and rebind sequence, subsequent network transmission may crash the system or corrupt kernel memory. The supplied score is 7.8 (High), but exposure appears limited to systems using the affected USB gadget functionality.

Executive priority

Treat as an expedited priority for products using USB NCM gadget mode, particularly embedded or physically accessible devices. For general Linux servers without this functionality, first confirm applicability before emergency action. No active exploitation is established in the supplied evidence.

Technical view

In Linux USB gadget f_ncm, an endpoint-enable error can prevent gether_disconnect() during NCM disable. Unbinding then frees the NCM object while dev->port_usb retains a stale pointer. After rebinding, eth_start_xmit() can dereference that freed object. The fix disconnects based on ncm->netdev rather than endpoint-enabled state.

Likely exposure

Most relevant to Linux devices configured for USB gadget NCM networking, including embedded systems and appliances. The supplied affected entries identify versions 4.4, 5.15.157, 6.1.88, 6.6.29, 6.8.8, and 6.9; the additional “0” entry is ambiguous. Distribution backports require vendor-specific verification.

Exploitation context

The supplied CVSS vector describes local, low-privilege exploitation without user interaction and potentially high confidentiality, integrity, and availability impact. Triggering requires a USB endpoint transport error followed by NCM unbind, rebind, and traffic. The bundle marks KEV false and provides no evidence of active exploitation or a public exploit.

Researcher notes

The failure depends on a narrow cleanup-state inconsistency: gether_disconnect() was gated by in_ep->enabled even though the network association could already exist. The correction instead tests ncm->netdev. The sources demonstrate a kernel paging fault, but do not establish reliable privilege escalation, remote reachability, exploit availability, or attacks in the wild.

Mitigation direction

  • Upgrade to a vendor-supported kernel or package containing the referenced f_ncm fix.
  • Prioritize embedded and appliance systems that expose USB NCM gadget networking.
  • If immediate patching is unavailable, consult vendor guidance for supported risk-reduction measures.
  • Avoid relying solely on version numbers because distributions may backport the correction.

Validation and detection

  • Inventory systems using Linux USB gadget NCM networking or the f_ncm function.
  • Record running kernel and distribution package versions on identified systems.
  • Confirm vendor advisories or package changelogs state that CVE-2024-26996 is fixed.
  • Where source provenance is available, verify inclusion of the applicable referenced stable-kernel commit.
  • After updating, confirm the intended fixed kernel is running.
Prepared
Confidence
high
Sources
7

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

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CVE-2024-26996 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
2ADP providers
9Source 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
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-2024-26996Attack 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
other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b, 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b, 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b, 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41b, 6b4012a2e4d4702f8fb0ee1db1c0f0b17ab7d41bunaffected
LinuxLinux4.4, 0, 5.15.157, 6.1.88, 6.6.29, 6.8.8, 6.9affected
Weakness

CWE details

No CWE listed

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