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Review reviewHigh

CVE-2021-47222

Linux Linux, linux kernel

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix vlan tunnel dst refcnt when egressing The egress tunnel code uses dst_clone() and directly sets the result which is wrong because the entry might have 0 refcnt or be already deleted, causing number of problems. It also triggers the WARN_ON() in dst_hold()[1] when a refcnt couldn't be taken. Fix it by using dst_hold_safe() and checking if a reference was actually taken before setting the dst. [1] dmesg WARN_ON log and following refcnt errors WARNING: CPU: 5 PID: 38 at include/net/dst.h:230 br_handle_egress_v...

CVSS
7.8
EPSS
0.25%
15.8% percentile
CISA KEV
Not listed
Published
2024.05.22
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.25%
Technical severityCVSS 7.8

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix vlan tunnel dst refcnt when egressing The egress tunnel code uses dst_clone() and directly sets the result which is wrong because the entry might have 0 refcnt or be already deleted, causing number of problems. It also triggers the WARN_ON() in dst_hold()[1] when a refcnt couldn't be taken. Fix it by using dst_hold_safe() and checking if a reference was actually taken before setting the dst. [1] dmesg WARN_ON log and following refcnt errors WARNING: CPU: 5 PID: 38 at include/net/dst.h:230 br_handle_egress_v...

Affected product and versions

Product
Linux Linux, linux kernel
Affected versions
>= 11538d039ac6efcf4f1a6c536e1b87cd3668a9fd < 42020f7f37a90d24b9551f5f7eba3f7c7c102968, >= 11538d039ac6efcf4f1a6c536e1b87cd3668a9fd < 84fc1c944e45ab317e2e70a0e7f76fa2a5e43b6e, >= 11538d039ac6efcf4f1a6c536e1b87cd3668a9fd < 79855be6445b6592bddb7bd7167083ec8cdbd73f, >= 11538d039ac6efcf4f1a6c536e1b87cd3668a9fd < fc7fdd8c5c2ad2fe3e297698be9d4dbe4a4e0579, >= 11538d039ac6efcf4f1a6c536e1b87cd3668a9fd < 25053a8404ba17ca48f5553d487afc1882e9f56c, >= 11538d039ac6efcf4f1a6c536e1b87cd3668a9fd < cfc579f9d89af4ada58c69b03bcaa4887840f3b3, >= 4.11, >= 4.11 < 4.14.238, >= 4.15 < 4.19.196, >= 4.20 < 5.4.128, >= 5.5 < 5.10.46, >= 5.11 < 5.12.13, 5.13
Fixed versions
4.14.238, 4.19.196, 5.4.128, 5.10.46, 5.12.13

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux Linux, linux kernel and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-416