critical 9.8

CVE-2026-89541 in the critical feed json

SUNRPC: harden gss_unwrap_resp_priv length checks

published 2026-09-11 58 d ago modified 2026-10-19 21 d ago also EUVD-2026-76452

cvss: 9.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits: 0; none known

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

gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with

offset = (u8 *)(p) - (u8 *)head->iov_base; if (offset + opaque_len > rcv_buf->len) goto unwrap_failed; maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, offset + opaque_len, rcv_buf);

Both operands are u32 and the sum is computed in u32. A reply with opaque_len near 0xffffffff makes offset + opaque_len wrap to a small value that is below rcv_buf->len, so the bound check passes and gss_unwrap() is called with end < begin. The check also lacks a lower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is accepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt header reads at ptr+4 and ptr+6 then run past the token.

A krb5p NFS server returning a crafted RPCSEC_GSS reply can drive the client into out-of-bounds reads in gss_krb5_unwrap_v2() and the rotate_left() loop that follows.

Fix by replacing the single combined check with three guards that are safe in u32 arithmetic and that enforce the RFC 4121 minimum outer token length:

if (offset > rcv_buf->len) goto unwrap_failed; if (opaque_len > rcv_buf->len - offset) goto unwrap_failed; if (opaque_len < GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed;

The first guard makes the subtraction in the second guard unconditionally safe; offset is derived from a successful xdr_inline_decode() in the head kvec, so in practice it already satisfies the bound. The floor mirrors the server-side check added in commit 5b757c2e57a5 ("SUNRPC: svcauth_gss: enforce krb5 token minimum length").

Patch / fix

fixed in 1 distros 5 links 8

Linux Linux 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3

debian ubuntu suse opensuse azure linux

linux Debian 12 6.1.190-1
linux Debian 13 6.12.111-1
linux Debian 14 7.2.6-1
linux-6.12 Debian 12 6.12.111-1~deb12u1

debian advisories DEBIAN-CVE-2026-89541

linux Ubuntu 22.04 LTS 5.15.0-202.212
linux Ubuntu 26.04 LTS 7.0.0-42.42
linux-aws Ubuntu 22.04 LTS 5.15.0-1119.126
linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
linux-gcp Ubuntu 22.04 LTS 5.15.0-1120.130
linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
linux-gke Ubuntu 22.04 LTS 5.15.0-1115.121
linux-ibm Ubuntu 22.04 LTS 5.15.0-1113.117

ubuntu advisories UBUNTU-CVE-2026-89541

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.84.1
kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.84.1
kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1
kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.84.1
kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.84.1.150700.17.47.1

suse advisories SUSE-SU-2026:4706-1 SUSE-SU-2026:4640-1 SUSE-SU-2026:24316-1 SUSE-SU-2026:24315-1 SUSE-SU-2026:24181-1 SUSE-SU-2026:24182-1

kernel-rt openSUSE Leap 16.0 6.12.0-160000.39.1
dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-64kb openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-syms openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-azure openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-source openSUSE Leap 16.0 6.12.0-160000.39.1
kernel-default openSUSE Leap 16.0 6.12.0-160000.39.1

opensuse advisories openSUSE-SU-2026:22091-1 openSUSE-SU-2026:11880-1

kernel Azure Linux 3.0 6.6.157.1-1

azure linux advisories AZL-100877

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-89541 updated 2026-11-06 cvss 6.5

kernel: SUNRPC: harden gss_unwrap_resp_priv length checks

Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
affected: workaround, no fix planned “Out of support scope”
Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: total
Assessed: 23 d ago (2026-10-16)

Exploit prediction

0.51% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Linux Linux

Classification

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2026-89541
NVD CVE-2026-89541

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary