CVE-2021-47307Network attack vector

Remote kernel crash via NULL DFS referral node

Published May 21, 2024 · Updated Aug 5, 2026

NULL pointer dereference in CIFS in Linux 2.6.28 through 5.13.4 allows remote attackers to crash the kernel via DFS referrals. During DFS referral handling, cifs_compose_mount_options() passes ref->node_name to cifs_build_devname() without checking whether the optional field is NULL, causing a kernel oops or panic. Reachability requires the CIFS client to mount or follow a referral from an attacker-controlled or compromised SMB/DFS server; the published impact is limited to availability.

CVSS severity7.5
High
EPSS probability0.68%
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 CIFS in Linux 2.6.28 through 5.13.4 allows remote attackers to crash the kernel via DFS referrals. During DFS referral handling, cifs_compose_mount_options() passes ref->node_name to cifs_build_devname() without checking whether the optional field is NULL, causing a kernel oops or panic. Reachability requires the CIFS client to mount or follow a referral from an attacker-controlled or compromised SMB/DFS server; the published impact is limited to availability.

The record

CVE
CVE-2021-47307
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=2.6.28
  2. Affected versionversion=2c55608f28444c3f33b10312881384c470ceed56 <03313d1c3a2f086bb60920607ab79ac8f8578306
  3. Affected versionversion=2c55608f28444c3f33b10312881384c470ceed56 <ae3d181f4e912f51af7776ea165f199b16fc165d
  4. Affected versionversion=2c55608f28444c3f33b10312881384c470ceed56 <e58c162789becede894d3e94c0ce6695a2ef5796
  5. Affected versionversion=2c55608f28444c3f33b10312881384c470ceed56 <f7d1fa65e74263d11f90ddd33b4d4cd905a93759

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.28; version=2c55608f28444c3f33b10312881384c470ceed56 <03313d1c3a2f086bb60920607ab79ac8f8578306; version=2c55608f28444c3f33b10312881384c470ceed56 <ae3d181f4e912f51af7776ea165f199b16fc165d; version=2c55608f28444c3f33b10312881384c470ceed56 <e58c162789becede894d3e94c0ce6695a2ef5796; version=2c55608f28444c3f33b10312881384c470ceed56 <f7d1fa65e74263d11f90ddd33b4d4cd905a93759

Published CVSS scores

7.5Linux CNACVSS:3.1/AV:N/AC:L/PR:N/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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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