Unity Linux 20.1070e Security Update: kernel (UTSA-2026-142541)

critical Nessus Plugin ID 370677

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-2026-142541 advisory.

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

SUNRPC: harden gss_krb5_unwrap_v2 against short tokens

gss_krb5_unwrap_v2() reads the EC and RRC header fields at ptr+4 and ptr+6 before validating that the token is at least GSS_KRB5_TOK_HDR_LEN (16) bytes long, and its rotate_left() helper passes buf->len - base to xdr_buf_subsegment() without verifying that base <= buf->len. When a caller hands in a sub-16-byte token, or a token whose declared len leaves base past the end of the buffer, three distinct failures follow:

gss_krb5_unwrap_v2(offset, len, buf) ptr = buf->head[0].iov_base + offset ec = *(ptr + 4) /* OOB read on short head */ rrc = *(ptr + 6) /* OOB read on short head */ rotate_left(offset + 16, buf, rrc) xdr_buf_subsegment(buf, &subbuf, base, buf->len - base) /* u32 wrap when base > len */
_rotate_left(&subbuf, shift) shift %= buf->len /* divide-by-zero when base == len */

After decryption, the cleanup arithmetic has the same shape:

movelen = min_t(unsigned int, buf->head[0].iov_len, len);
movelen -= offset + GSS_KRB5_TOK_HDR_LEN + headskip;
BUG_ON(offset + GSS_KRB5_TOK_HDR_LEN + headskip + movelen > buf->head[0].iov_len);

The BUG_ON re-adds the value just subtracted, so it reduces to min(A, B) > A and is permanently false; it cannot catch the unsigned underflow of movelen, which then drives a ~UINT_MAX-byte memmove().

Add four defense-in-depth guards inside the unwrap core so it is safe regardless of what its callers validate:

- reject tokens with len - offset < GSS_KRB5_TOK_HDR_LEN before touching ptr+4/ptr+6;
- bail from rotate_left() when buf->len <= base, covering both the underflow and zero-length cases;
- return early from _rotate_left() when buf->len is zero, so the shift %= buf->len modulo cannot fault;
- replace the dead BUG_ON with a live check that returns GSS_S_DEFECTIVE_TOKEN before the movelen subtraction.

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: Critical

ID: 370677

File Name: unity_linux_UTSA-2026-142541.nasl

Version: 1.1

Type: Local

Family: Unity Linux Local Security Checks

Published: 10/22/2026

Updated: 10/22/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.42

CVSS v2

Risk Factor: Critical

Base Score: 10

Temporal Score: 7.4

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

CVSS Score Source: CVE-2026-89542

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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: 10/22/2026

Vulnerability Publication Date: 9/11/2026

Reference Information

CVE: CVE-2026-89542

Detections

Analytics