CVE-2026-98171: smb: client: fix next_buffer UAF and NextCommand bounds in compound PDUs
In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix nextbuffer UAF and NextCommand bounds in compound PDUs
Fix several related bounds checking and pointer lifecycle issues in receiveencryptedstandard()'s handling of compound encrypted frames:
- Clear nextbuffer after assigning it to server->bigbuf. A stale nextbuffer pointer can lead to a use-after-free on subsequent error paths. - Update pdulength to the decrypted plaintext size (bufsize). Using the pre-decryption length allows NextCommand to point into stale ciphertext residue. - Reject nextcmd values smaller than MIDHEADERSIZE(server). - Fix an integer overflow in the upper bound check by verifying pdulength - nextcmd < MIDHEADERSIZE(server), ensuring the trailing slice is large enough for a header.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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Fixed in 6.6.158.1-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.113-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 7.2.8-1 - Upgrade
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debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.113-1~deb12u1 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 5.10.273 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 5.15.224 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.1.189 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.6.158 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.12.112 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.18.54 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 7.2.8 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.190-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-42.42 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1016.17 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1016.18 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1015.16 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1
Event History
Frequently Asked Questions
Which systems are affected?
Systems using the Linux kernel SMB client are affected when they process compound encrypted SMB frames. The issue is in receive_encrypted_standard() handling of those frames.
What traffic condition is required to trigger the issue?
The vulnerable code path involves compound encrypted SMB protocol data units with NextCommand values. The fixes address stale pointer handling after errors and insufficient validation of NextCommand bounds against the decrypted plaintext length.