CVE-2021-47103 remediation guide

Linux Linux, linux kernel

In the Linux kernel, the following vulnerability has been resolved: inet: fully convert sk->sk_rx_dst to RCU rules syzbot reported various issues around early demux, one being included in this changelog [1] sk->sk_rx_dst is using RCU protection without clearly documenting it. And following sequences in tcp_v4_do_rcv()/tcp_v6_do_rcv() are not following standard RCU rules. [a] dst_release(dst); [b] sk->sk_rx_dst = NULL; They look wrong because a delete operation of RCU protected pointer is supposed to clear the pointer before the call_rcu()/synchronize_rcu() guarding actual memory freeing. In...

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ProductLinux Linux, linux kernel

Affected versions>= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 68c34ce11ef23328692aa35fa6aaafdd75913100, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 92e6e36ecd16808866ac6172b9491b5097cde449, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 75a578000ae5e511e5d0e8433c94a14d9c99c412, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < c3bb4a7e8cbc984e1cdac0fe6af60e880214ed6e, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < f039b43cbaea5e0700980c2f0052da05a70782e0, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 0249a4b8a554f2eb6a27b62516fa50168584faa4, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 8f905c0e7354ef261360fb7535ea079b1082c105, >= 3.6, >= 3.6 < 4.9.331, >= 4.10 < 4.14.296, >= 4.15 < 4.19.262, >= 4.20 < 5.4.220, >= 5.5 < 5.10.150, >= 5.11 < 5.15.12, 5.16

Fixed versions4.9.331, 4.14.296, 4.19.262, 5.4.220, 5.10.150, 5.15.12

Priority basisReview · CVSS 7.8 · EPSS 0.95%

Identify the affected asset

Confirm whether Linux Linux, linux kernel is installed, record the deployed version and installation path, and identify exposed interfaces.

Record the product name, package or appliance identifier, and installed version.
Identify internet-facing, administrative, API, and internal access paths.
Preserve the pre-change configuration and relevant service logs.

Validate the affected-version match

Compare the deployed version with the affected range: >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 68c34ce11ef23328692aa35fa6aaafdd75913100, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 92e6e36ecd16808866ac6172b9491b5097cde449, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 75a578000ae5e511e5d0e8433c94a14d9c99c412, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < c3bb4a7e8cbc984e1cdac0fe6af60e880214ed6e, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < f039b43cbaea5e0700980c2f0052da05a70782e0, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 0249a4b8a554f2eb6a27b62516fa50168584faa4, >= 41063e9dd11956f2d285e12e4342e1d232ba0ea2 < 8f905c0e7354ef261360fb7535ea079b1082c105, >= 3.6, >= 3.6 < 4.9.331, >= 4.10 < 4.14.296, >= 4.15 < 4.19.262, >= 4.20 < 5.4.220, >= 5.5 < 5.10.150, >= 5.11 < 5.15.12, 5.16. Treat incomplete inventory results as unresolved.

Prioritize with independent signals

The CVSS severity warrants an early asset and exposure review. Combine this signal with asset criticality, exposure, compensating controls, and business impact.

Apply supported remediation

Follow the vendor advisory or supported update path. Current fixed-version status: 4.9.331, 4.14.296, 4.19.262, 5.4.220, 5.10.150, 5.15.12. Preserve configuration and rollback material before change.

Verify the result

Confirm the resulting version, service health, authentication and access paths, monitoring coverage, and relevant security logs.

Confirm the expected version and package state.
Run a functional health check for critical service paths.
Review authentication, error, application, and security monitoring logs.
Reassess exposure if the supported fix cannot be applied.

Operational boundary

This page does not replace the vendor advisory, support contract, change-management process, or recovery plan. Do not infer that an asset is unaffected from an incomplete inventory query or a missing fixed-version field.