---
id: CVE-2026-72466
title: 'xprtrdma: Fix bcall rep leak and unbounded peek'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xprtrdma: Fix bcall rep leak and unbounded peek

  rpcrdma_is_bcall() decodes a reply's first words to decide whether
  the frame is a backchannel call. Two issues in that …
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    0cee8f9c3b14bd6dee9c4310090a7f45b89b834f
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    7afc2f8d2fd9394724df9eaf22ce7a71029a5fba
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    88b5346284a184a6b7d019912232a571d672d3e3
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    07aa506436be7634e381e1e1f6d0efa9efc81ecc
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    d7a2870dde3bb09d51d6b9c877642996ad6b92dd
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    118a16a18c59f7ad8084b2d13988839b669fca10
  - >-
    Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 <
    c7653d5cebc8492c77ec0415b5e9c0fb3e644bc6
  - Linux 4.14
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T18:50:23.646833Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:25.296Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72466'
references:
  - url: 'https://git.kernel.org/stable/c/0cee8f9c3b14bd6dee9c4310090a7f45b89b834f'
  - url: 'https://git.kernel.org/stable/c/7afc2f8d2fd9394724df9eaf22ce7a71029a5fba'
  - url: 'https://git.kernel.org/stable/c/88b5346284a184a6b7d019912232a571d672d3e3'
  - url: 'https://git.kernel.org/stable/c/07aa506436be7634e381e1e1f6d0efa9efc81ecc'
  - url: 'https://git.kernel.org/stable/c/d7a2870dde3bb09d51d6b9c877642996ad6b92dd'
  - url: 'https://git.kernel.org/stable/c/118a16a18c59f7ad8084b2d13988839b669fca10'
  - url: 'https://git.kernel.org/stable/c/c7653d5cebc8492c77ec0415b5e9c0fb3e644bc6'
tags:
  - cve.org
epss: 0.00738
epssPercentile: 0.53608
ingestedAt: '2026-10-16T19:46:24.393Z'
---

## Overview

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

xprtrdma: Fix bcall rep leak and unbounded peek

rpcrdma_is_bcall() decodes a reply's first words to decide whether
the frame is a backchannel call. Two issues in that decode path
let a short or malformed reply leak the receive buffer and drain
the Receive queue.

First, the speculative peek

    p = xdr_inline_decode(xdr, 0);
    /* five p++ reads follow */

asks xdr_inline_decode() for zero bytes, which returns xdr->p
without consulting xdr->end. The five subsequent __be32 reads can
then walk up to 20 bytes past the wire payload into stale regbuf
contents and misclassify the reply as a backchannel call.

Second, after the post-peek

    p = xdr_inline_decode(xdr, 3 * sizeof(*p));
    if (unlikely(!p))
            return true;

the short-header arm returns true without calling
rpcrdma_bc_receive_call(). The contract with the caller is that a
true return transfers ownership of rep to the backchannel path:

    rpcrdma_reply_handler()
      if (rpcrdma_is_bcall(r_xprt, rep))
              return;        /* bare return, skips out_post */
      ...
    out_post:
      rpcrdma_post_recvs(r_xprt, credits + ...);

Because rpcrdma_bc_receive_call() never ran, no one took rep, but
rpcrdma_reply_handler still bare-returns past rpcrdma_rep_put()
and rpcrdma_post_recvs(). The rep, with its persistently
DMA-mapped receive buffer, is orphaned on rb_all_reps and freed
only at transport teardown. This completion reposts nothing, so
its slot is reclaimed only when a later forward-channel reply
reaches out_post and rpcrdma_post_recvs() allocates a fresh rep to
backfill; absent that traffic the Receive queue drains and the
peer's Sends draw RNR NAKs.

Fix by consulting xdr->end after the zero-length peek so the five
__be32 reads cannot run unless 20 bytes of wire payload remain. A
byte-precise comparison against xdr->end is required because a
non-4-aligned receive rounds the stream's word count up past the
true payload. Also return false from the short-header arm so the
reply falls through the normal out_norqst cleanup chain
(rpcrdma_rep_put() plus rpcrdma_post_recvs()).

## Affected

- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < 0cee8f9c3b14bd6dee9c4310090a7f45b89b834f`
- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < 7afc2f8d2fd9394724df9eaf22ce7a71029a5fba`
- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < 88b5346284a184a6b7d019912232a571d672d3e3`
- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < 07aa506436be7634e381e1e1f6d0efa9efc81ecc`
- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < d7a2870dde3bb09d51d6b9c877642996ad6b92dd`
- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < 118a16a18c59f7ad8084b2d13988839b669fca10`
- `Linux >= 41c8f70f5a3db7e06179186b6525fd9ee1d7d314 < c7653d5cebc8492c77ec0415b5e9c0fb3e644bc6`
- `Linux 4.14`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.