What’s Vulnerable › Vulnerabilities

CVE-2026-98171: smb: client: fix next_buffer UAF and NextCommand bounds in compound PDUs

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-06 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix next_buffer UAF and NextCommand bounds in compound PDUs Fix several related bounds checking and pointer lifecycle issues in receive_encrypted_standard()'s handling of compound encrypted frames: - Clear next_buffer after assigning it to server->bigbuf. A stale next_buffer pointer can lead to a use-after-free on subsequent error paths. - Update pdu_length to the decrypted plaintext size (buf_size). Using the pre-decryption length allows NextCommand to point into stale ciphertext residue. - Reject next_cmd values smaller than MID_HEADER_SIZE(server). - Fix an integer overflow in the upper bound check by verifying pdu_length - next_cmd < MID_HEADER_SIZE(server), ensuring the trailing slice is large enough for a header.

Affected products

• Linux: 4.19 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/05762c5bc1cfdcac36747994fde2c04387a457f1
• https://git.kernel.org/stable/c/1ed29f7a03417b405f38c09cfe04124883127b53
• https://git.kernel.org/stable/c/491e33144dee872cffda207f6fcb09260728f803
• https://git.kernel.org/stable/c/72eaef1f37a3b6bec11c342736834dc3707be3e4
• https://git.kernel.org/stable/c/7f022867ec9f0166a0b4400385bb601b1c6b2c75
• https://git.kernel.org/stable/c/858d5ac22cb889266993e7670f9f0c4f4aeedd78
• https://git.kernel.org/stable/c/8749946579708ea0d339034bb7f423a67dbe89cf
• https://git.kernel.org/stable/c/96c436e4b010711452b2872558938f4ef276492a

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