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CVE Record

CVE-2025-40071: tty: n_gsm: Don't block input queue by waiting MSC

In the Linux kernel, the following vulnerability has been resolved: tty: n_gsm: Don't block input queue by waiting MSC Currently gsm_queue() processes incoming frames and when opening a DLC channel it calls gsm_dlci_open() which calls gsm_modem_update(). If basic mode is used it calls gsm_modem_upd_via_msc() and it cannot block the input queue by waiting the response to come into the same input queue. Instead allow sending Modem Status Command without waiting for remote end to respond. Define a new function gsm_modem_send_initial_msc() for this purpose. As MSC is only valid for basic encoding, it does not do anything for advanced or when convergence layer type 2 is used.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects the tty n_gsm driver. In a specific channel-opening path, the kernel could wait for a modem status response that must arrive through the same input queue it is blocking. The practical impact is not fully described in the sources, and no CVSS score is provided.

Executive priority

Monitor and patch through normal kernel maintenance, escalating for modem-connected, embedded, or telecom-adjacent systems. The available evidence does not justify emergency treatment without proof of exposure or exploitation.

Technical view

gsm_queue() processes incoming frames and may call gsm_dlci_open(), then gsm_modem_update(). In basic mode, gsm_modem_upd_via_msc() could wait for an MSC response on the same input queue, blocking progress. The fix sends the initial MSC without waiting; it is not used for advanced encoding or convergence layer type 2.

Likely exposure

Exposure appears limited to Linux systems running affected kernels where tty n_gsm/GSM multiplexing functionality is present and used. The bundle lists Linux as affected but does not identify specific distributions, appliances, or configurations. Systems not using this subsystem are likely lower priority pending vendor guidance.

Exploitation context

The bundle does not report active exploitation, public exploit code, or KEV listing. It describes an upstream kernel logic flaw and stable kernel fixes. Treat exploitation impact as unconfirmed from the provided evidence.

Researcher notes

Evidence supports a queue-blocking bug in tty/n_gsm basic-mode MSC handling. The sources do not provide CVSS, CWE, exploitability analysis, privilege requirements, or attack surface details. Avoid broad impact claims until vendor advisories add severity context.

Mitigation direction

  • Apply vendor kernel updates containing the referenced stable fixes.
  • Prioritize systems using tty n_gsm or modem multiplexing workflows.
  • Consult Linux distribution advisories for backported fix status.
  • Track vendor CVE updates because severity data is currently incomplete.

Validation and detection

  • Inventory Linux kernel versions across affected assets.
  • Confirm whether n_gsm functionality is enabled or used.
  • Compare deployed kernels with vendor-fixed builds or referenced stable commits.
  • Regression test modem or GSM multiplexing workflows after patching.
Prepared
Confidence
medium
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

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CVE-2025-40071 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
5Source 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
LinuxLinux48473802506d2d6151f59e0e764932b33b53cb3b, 48473802506d2d6151f59e0e764932b33b53cb3b, 48473802506d2d6151f59e0e764932b33b53cb3b, 48473802506d2d6151f59e0e764932b33b53cb3b, 920e849b7d23ced84c9d11e11e2449e34973cfb8, e83b4e1540469babeffcfd44a605cf8a61542598, 5.15.54, 5.17.6unaffected
LinuxLinux5.18, 0, 6.6.112, 6.12.53, 6.17.3, 6.18affected
Weakness

CWE details

No CWE listed

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