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Unity Linux 20.1070a Security Update: kernel (UTSA-2025-988850)

medium Nessus Plugin ID 273057

Synopsis

The Unity Linux host is missing one or more security updates.

Description

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2025-988850 advisory.

 In the Linux kernel, the following vulnerability has been resolved:

 mptcp: clear 'kern' flag from fallback sockets

 The mptcp ULP extension relies on sk->sk_sock_kern being set correctly:
 It prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, mptcp, 6); from working for plain tcp sockets (any userspace-exposed socket).

 But in case of fallback, accept() can return a plain tcp sk.
 In such case, sk is still tagged as 'kernel' and setsockopt will work.

 This will crash the kernel, The subflow extension has a NULL ctx->conn mptcp socket:

 BUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0 Call Trace:
 tcp_data_ready+0xf8/0x370 [..]

Tenable has extracted the preceding description block directly from the Unity Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Update the affected kernel package.

See Also

http://www.nessus.org/u?3472f0e1

http://www.nessus.org/u?853b4a20

https://nvd.nist.gov/vuln/detail/CVE-2021-47593

Plugin Details

Severity: Medium

ID: 273057

File Name: unity_linux_UTSA-2025-988850.nasl

Version: 1.1

Type: local

Published: 11/5/2025

Updated: 11/5/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.4

Vector: CVSS2#AV:L/AC:L/Au:S/C:N/I:N/A:C

CVSS Score Source: CVE-2021-47593

CVSS v3

Risk Factor: Medium

Base Score: 5.5

Temporal Score: 4.8

Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 11/5/2025

Vulnerability Publication Date: 1/28/2022

Reference Information

CVE: CVE-2021-47593