CVE-2020-36789

Service interruption via unsafe CAN skb freeing

Published Apr 17, 2025 · Updated May 11, 2026

NULL pointer dereference in Linux before 5.10 allows local users to interrupt service through congested CAN traffic. The CAN echo path can pass an skb to netif_rx(), whose enqueue_to_backlog() path calls kfree_skb() in hard IRQ context instead of an IRQ-safe freeing routine. Reachability requires a CAN driver to call can_get_echo_skb() during a hardware interrupt while the network backlog is congested.

CVSS severity5.5
Medium
EPSS probability0.19%
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 before 5.10 allows local users to interrupt service through congested CAN traffic. The CAN echo path can pass an skb to netif_rx(), whose enqueue_to_backlog() path calls kfree_skb() in hard IRQ context instead of an IRQ-safe freeing routine. Reachability requires a CAN driver to call can_get_echo_skb() during a hardware interrupt while the network backlog is congested.

The record

CVE
CVE-2020-36789
Published
Apr 17, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 17, 2025CVE 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=2.6.31
  2. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <2283f79b22684d2812e5c76fc2280aae00390365
  3. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <248b71ce92d4f3a574b2537f9838f48e892618f4
  4. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <3a922a85701939624484e7f2fd07d32beed00d25
  5. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <451187b20431924d13fcfecc500d7cd2d9951bac
  6. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22
  7. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <87530b557affe01c764de32dbeb58cdf47234574
  8. Affected versionversion=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <ab46748bf98864f9c3f5559060bf8caf9df2b41e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.31; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <2283f79b22684d2812e5c76fc2280aae00390365; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <248b71ce92d4f3a574b2537f9838f48e892618f4; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <3a922a85701939624484e7f2fd07d32beed00d25; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <451187b20431924d13fcfecc500d7cd2d9951bac; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <7e4cf2ec0ca236c3e5f904239cec6efe1f3baf22; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <87530b557affe01c764de32dbeb58cdf47234574; version=39549eef3587f1c1e8c65c88a2400d10fd30ea17 <ab46748bf98864f9c3f5559060bf8caf9df2b41e

Published CVSS scores

5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CanonicalCVSS: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 exploitUnconfirmed

Weakness, pattern, technique

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

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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