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Unity Linux 20.1070e Security Update: kernel (UTSA-2026-005500)
medium Nessus Plugin ID 300459
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-2026-005500 advisory.In the Linux kernel, the following vulnerability has been resolved:
net_sched: hfsc: Address reentrant enqueue adding class to eltree twice
Savino says:
We are writing to report that this recent patch (141d34391abbb315d68556b7c67ad97885407547) [1] can be bypassed, and a UAF can still occur when HFSC is utilized with NETEM.
The patch only checks the cl->cl_nactive field to determine whether it is the first insertion or not [2], but this field is only incremented by init_vf [3].
By using HFSC_RSC (which uses init_ed) [4], it is possible to bypass the check and insert the class twice in the eltree.
Under normal conditions, this would lead to an infinite loop in hfsc_dequeue for the reasons we already explained in this report [5].
However, if TBF is added as root qdisc and it is configured with a very low rate, it can be utilized to prevent packets from being dequeued.
This behavior can be exploited to perform subsequent insertions in the HFSC eltree and cause a UAF.
To fix both the UAF and the infinite loop, with netem as an hfsc child, check explicitly in hfsc_enqueue whether the class is already in the eltree whenever the HFSC_RSC flag is set.
[1] https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=141d34391abbb315d685 56b7c67ad97885407547 [2] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L1572 [3] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L677 [4] https://elixir.bootlin.com/linux/v6.15-rc5/source/net/sched/sch_hfsc.c#L1574 [5] https://lore.kernel.org/netdev/8DuRWwfqjoRDLDmBMlIfbrsZg9Gx50DHJc1ilxsEBNe2D6NMoigR_eIRIG0LOjMc3r10nUU [email protected]/T/#u
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?b968ee2f
Plugin Details
Severity: Medium
ID: 300459
File Name: unity_linux_UTSA-2026-005500.nasl
Version: 1.1
Type: local
Published: 3/3/2026
Updated: 3/3/2026
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 5.1
CVSS v2
Risk Factor: Medium
Base Score: 4.6
Temporal Score: 3.6
Vector: CVSS2#AV:L/AC:L/Au:S/C:N/I:N/A:C
CVSS Score Source: CVE-2025-38001
CVSS v3
Risk Factor: Medium
Base Score: 5.5
Temporal Score: 5
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:P/RL:O/RC:C
Vulnerability Information
Required KB Items: Host/local_checks_enabled, Host/UOS-Server/release, Host/UOS-Server/rpm-list, Host/cpu
Exploit Available: true
Exploit Ease: Exploits are available
Patch Publication Date: 3/2/2026
Vulnerability Publication Date: 6/6/2025
Reference Information
CVE: CVE-2025-38001