CVE-2020-27830Public exploit

System crash via uninitialized Speakup synthesizer dereference

Published May 13, 2021 · Updated Aug 4, 2024

NULL pointer dereference in Linux Kernel 5.9.11 allows local users to crash the system through the Speakup line discipline. The spk_ttyio_receive_buf2() callback dereferences spk_ttyio_synth after user space selects the exposed line discipline, without verifying that the synthesizer pointer is initialized. A local account with access to /dev/tty1 and the required TTY ioctls can trigger a kernel panic; the published reproduction enabled accessibility, Speakup, and KASAN.

CVSS severity5.5
Medium
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Linux Kernel 5.9.11 allows local users to crash the system through the Speakup line discipline. The spk_ttyio_receive_buf2() callback dereferences spk_ttyio_synth after user space selects the exposed line discipline, without verifying that the synthesizer pointer is initialized. A local account with access to /dev/tty1 and the required TTY ioctls can trigger a kernel panic; the published reproduction enabled accessibility, Speakup, and KASAN.

The record

CVE
CVE-2020-27830
Published
May 13, 2021
Updated
Aug 4, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=kernel 5.9.14

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=kernel 5.9.14

Published CVSS scores

5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

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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