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CVE Record

CVE-2021-46905: net: hso: fix NULL-deref on disconnect regression

In the Linux kernel, the following vulnerability has been resolved: net: hso: fix NULL-deref on disconnect regression Commit 8a12f8836145 ("net: hso: fix null-ptr-deref during tty device unregistration") fixed the racy minor allocation reported by syzbot, but introduced an unconditional NULL-pointer dereference on every disconnect instead. Specifically, the serial device table must no longer be accessed after the minor has been released by hso_serial_tty_unregister().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-46905 is a Linux kernel bug in the hso network/serial driver. A prior fix introduced a NULL-pointer dereference during device disconnect, which can crash affected systems using that driver. The source bundle does not provide CVSS, CWE, confirmed exploit activity, or distro-specific impact.

Executive priority

Prioritize patching where Linux hosts use hso-supported devices or show related kernel crashes. For general fleets without this driver path, treat as routine kernel hygiene unless vendor guidance raises severity.

Technical view

The flaw is a disconnect-path regression in Linux net/hso. After hso_serial_tty_unregister() releases the minor, the serial device table must not be accessed. The vulnerable behavior was introduced by commit 8a12f8836145 and corrected in referenced stable kernel commits.

Likely exposure

Exposure is most likely on Linux systems with the hso driver present and relevant hardware or device paths active. Systems without that driver or hardware path are less likely exposed. Confirm using the running kernel version and vendor backport status.

Exploitation context

The bundle does not show CISA KEV listing or public active exploitation evidence. Available evidence supports a stability and denial-of-service concern on disconnect, not privilege escalation or remote code execution.

Researcher notes

Evidence is narrow but clear: the issue is a NULL dereference after minor release in the hso disconnect flow. The source bundle lacks CVSS, exploit prerequisites, and distro backport details, so exposure assessment depends on kernel build and driver usage.

Mitigation direction

  • Update to a vendor kernel that includes the referenced stable fixes.
  • Check distribution advisories for backported fixes before relying on upstream version numbers.
  • Reduce exposure to affected hso hardware or device paths where operationally feasible.
  • Monitor kernel logs for hso disconnect crashes until patched.

Validation and detection

  • Inventory Linux kernel versions across affected assets.
  • Confirm whether the hso driver is built, loaded, or used.
  • Map running kernels to vendor advisories or referenced stable commits.
  • Review kernel logs for NULL dereference events involving hso disconnect handling.
Prepared
Confidence
medium
Sources
11

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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CVE-2021-46905 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
2ADP providers
10Source links

SSVC decision data

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

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
LinuxLinuxa462067d7c8e6953a733bf5ade8db947b1bb5449, 145c89c441d27696961752bf51b323f347601bee, caf5ac93b3b5d5fac032fc11fbea680e115421b4, 92028d7a31e55d53e41cff679156b9432cffcb36, 4a2933c88399c0ebc738db39bbce3ae89786d723, dc195928d7e4ec7b5cfc6cd10dc4c8d87a7c72ac, 388d05f70f1ee0cac4a2068fd295072f1a44152a, 8a12f8836145ffe37e9c8733dce18c22fb668b66, 8a12f8836145ffe37e9c8733dce18c22fb668b66, 4.19.187, 5.4.112, 5.10.30, 5.11.14unaffected
LinuxLinux5.12, 0, 4.19.189, 5.4.115, 5.10.33, 5.11.17, 5.12.1, 5.13affected
Weakness

CWE details

No CWE listed

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