CVE-2026-89541 Affecting linux-6.12 package, versions <6.12.111-1~deb12u1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.51% (42nd percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-DEBIAN12-LINUX612-20506272
  • published5 Oct 2026
  • disclosed11 Sept 2026

Introduced: 11 Sep 2026

NewCVE-2026-89541  (opens in a new tab)

How to fix?

Upgrade Debian:12 linux-6.12 to version 6.12.111-1~deb12u1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream linux-6.12 package and not the linux-6.12 package as distributed by Debian. See How to fix? for Debian:12 relevant fixed versions and status.

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

SUNRPC: harden gss_unwrap_resp_priv length checks

gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with

offset = (u8 *)(p) - (u8 *)head-&gt;iov_base;
if (offset + opaque_len &gt; rcv_buf-&gt;len)
        goto unwrap_failed;
maj_stat = gss_unwrap(ctx-&gt;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 &gt; rcv_buf-&gt;len)
        goto unwrap_failed;
if (opaque_len &gt; rcv_buf-&gt;len - offset)
        goto unwrap_failed;
if (opaque_len &lt; 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").

CVSS Base Scores

version 3.1