Bug 2502518 (CVE-2026-64037) - CVE-2026-64037 kernel: wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
Summary: CVE-2026-64037 kernel: wifi: iwlwifi: mld: fix TSO segmentation explosion whe...
Keywords:
Status: NEW
Alias: CVE-2026-64037
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-19 17:03 UTC by OSIDB Bzimport
Modified: 2026-09-14 13:36 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:65334 0 None None None 2026-09-08 11:35:21 UTC
Red Hat Product Errata RHSA-2026:67150 0 None None None 2026-09-14 13:36:31 UTC

Description OSIDB Bzimport 2026-07-19 17:03:45 UTC
In the Linux kernel, the following vulnerability has been resolved:

wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled

When the TLC notification disables AMSDU for a TID, the MLD driver sets
max_tid_amsdu_len to the sentinel value 1. The TSO segmentation path in
iwl_mld_tx_tso_segment() checks for zero but not for this sentinel,
allowing it to reach the num_subframes calculation:

  num_subframes = (max_tid_amsdu_len + pad) / (subf_len + pad)
                = (1 + 2) / (1534 + 2) = 0

This zero propagates to iwl_tx_tso_segment() which sets:

  gso_size = num_subframes * mss = 0

Calling skb_gso_segment() with gso_size=0 creates over 32000 tiny
segments from a single GSO skb. This floods the TX ring with ~1024
micro-frames (the rest are purged), creating a massive burst of TX
completion events that can lead to memory corruption and a subsequent
use-after-free in TCP's retransmit queue (refcount underflow in
tcp_shifted_skb, NULL deref in tcp_rack_detect_loss).

The MVM driver is immune because it checks mvmsta->amsdu_enabled before
reaching the num_subframes calculation. The MLD driver has no equivalent
bitmap check and relies solely on max_tid_amsdu_len, which does not
catch the sentinel value.

Fix this by detecting the sentinel value (max_tid_amsdu_len == 1) at the
existing check and falling back to non-AMSDU TSO segmentation. Also add
a WARN_ON_ONCE guard after the num_subframes division as defense-in-depth
to catch any future code paths that produce zero through a different
mechanism.

Comment 5 errata-xmlrpc 2026-09-08 11:35:20 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:65334 https://access.redhat.com/errata/RHSA-2026:65334

Comment 6 Jon Orris 2026-09-14 13:36:30 UTC
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:67150 https://access.redhat.com/errata/RHSA-2026:67150


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