Unity Linux 20.1050e Security Update: kernel (UTSA-2026-102106)

medium Nessus Plugin ID 338594

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-2026-102106 advisory.

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

xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path

icmp_route_lookup() performs multiple route lookups to find a suitable route for sending ICMP error messages, with special handling for XFRM (IPsec) policies.

The lookup sequence is:
1. First, lookup output route for ICMP reply (dst = original src) 2. Pass through xfrm_lookup() for policy check 3. If blocked (-EPERM) or dst is not local, enter reverse path 4. In reverse path, call xfrm_decode_session_reverse() to get fl4_dec which reverses the original packet's flow (saddr<->daddr swapped) 5. If fl4_dec.saddr is local (we are the original destination), use
__ip_route_output_key() for output route lookup 6. If fl4_dec.saddr is NOT local (we are a forwarding node), use ip_route_input() to simulate the reverse packet's input path 7. Finally, pass rt2 through xfrm_lookup() with XFRM_LOOKUP_ICMP flag

The bug occurs in step 6: ip_route_input() is called with fl4_dec.daddr (original packet's source) as destination. If this address becomes local between the initial check and ip_route_input() call (e.g., due to concurrent ip addr add), ip_route_input() returns a LOCAL route with dst.output set to ip_rt_bug.

This route is then used for ICMP output, causing dst_output() to call ip_rt_bug(), triggering a WARN_ON:

------------[ cut here ]------------ WARNING: net/ipv4/route.c:1275 at ip_rt_bug+0x21/0x30, CPU#1 Call Trace:
<TASK> ip_push_pending_frames+0x202/0x240 icmp_push_reply+0x30d/0x430
__icmp_send+0x1149/0x24f0 ip_options_compile+0xa2/0xd0 ip_rcv_finish_core+0x829/0x1950 ip_rcv+0x2d7/0x420
__netif_receive_skb_one_core+0x185/0x1f0 netif_receive_skb+0x90/0x450 tun_get_user+0x3413/0x3fb0 tun_chr_write_iter+0xe4/0x220 ...

Fix this by checking rt2->rt_type after ip_route_input(). If it's RTN_LOCAL, the route cannot be used for output, so treat it as an error.

The reproducer requires kernel modification to widen the race window, making it unsuitable as a selftest. It is available at:

https://gist.github.com/mrpre/eae853b72ac6a750f5d45d64ddac1e81

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.

Plugin Details

Severity: Medium

ID: 338594

File Name: unity_linux_UTSA-2026-102106.nasl

Version: 1.1

Type: Local

Family: Unity Linux Local Security Checks

Published: 8/21/2026

Updated: 8/21/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.72

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-2026-45905

CVSS v3

Risk Factor: Medium

Base Score: 4.7

Temporal Score: 4.1

Vector: CVSS:3.0/AV:L/AC:H/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: 8/17/2026

Vulnerability Publication Date: 3/27/2026

Reference Information

CVE: CVE-2026-45905

Detections

Analytics