CVE-2021-47403

Carrier module unload prevention via reference leak

Published May 21, 2024 · Updated May 11, 2026

Reference leakage in the Linux kernel ipoctal driver allows local users to keep its carrier module loaded through repeated TTY opens. The ipoctal open path acquired a carrier-module reference for every open, while final TTY destruction released only one reference. Exploitation requires local access to an affected ipoctal TTY device; accumulated references leave the carrier module pinned.

CVSS severity7.1
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reference leakage in the Linux kernel ipoctal driver allows local users to keep its carrier module loaded through repeated TTY opens. The ipoctal open path acquired a carrier-module reference for every open, while final TTY destruction released only one reference. Exploitation requires local access to an affected ipoctal TTY device; accumulated references leave the carrier module pinned.

The record

CVE
CVE-2021-47403
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-200
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.18
  2. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <31398849b84ebae0d43a1cf379cb9895597f221a
  3. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <3253c87e1e5bc0107aab773af2f135ebccf38666
  4. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <7cea848678470daadbfdaa6a112b823c290f900c
  5. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <811178f296b16af30264def74c8d2179a72d5562
  6. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <9c5b77a7ffc983b2429ce158b50497c5d3c86a69
  7. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <bb8a4fcb2136508224c596a7e665bdba1d7c3c27
  8. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <c0adb5a947dec6cff7050ec56d78ecd3916f9ce6
  9. Affected versionversion=82a82340bab6c251e0705339f60763718eaa2a22 <dde4c1429b97383689f755ce92b4ed1e84a9c92b

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.18; version=82a82340bab6c251e0705339f60763718eaa2a22 <31398849b84ebae0d43a1cf379cb9895597f221a; version=82a82340bab6c251e0705339f60763718eaa2a22 <3253c87e1e5bc0107aab773af2f135ebccf38666; version=82a82340bab6c251e0705339f60763718eaa2a22 <7cea848678470daadbfdaa6a112b823c290f900c; version=82a82340bab6c251e0705339f60763718eaa2a22 <811178f296b16af30264def74c8d2179a72d5562; version=82a82340bab6c251e0705339f60763718eaa2a22 <9c5b77a7ffc983b2429ce158b50497c5d3c86a69; version=82a82340bab6c251e0705339f60763718eaa2a22 <bb8a4fcb2136508224c596a7e665bdba1d7c3c27; version=82a82340bab6c251e0705339f60763718eaa2a22 <c0adb5a947dec6cff7050ec56d78ecd3916f9ce6; version=82a82340bab6c251e0705339f60763718eaa2a22 <dde4c1429b97383689f755ce92b4ed1e84a9c92b
The Linux Kernel Organization · Linux Kernelversion=3.18; version=82a82340bab6

Published CVSS scores

7.1CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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