Critical severity · published Jul 19, 2026
CVE-2026-64037
wifi: iwlwifi: mld: fix TSO segmentation explosion when AMSDU is disabled
9.8
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 37% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
KE
Kernel · Linux
6.15 before 6.18.34; 6.19 before 7.0.11; 7.1; 7.1; 7.1; 7.1 · source: NVD
LI
Linux · Linux
d1e879ec600f9b3bdd253167533959facfefb17b before 9e360e610a73f62432e986775023d5382773f045; d1e879ec600f9b3bdd253167533959facfefb17b before cbe1c8245e4469d1aa6e12e5d913611376d23788; d1e879ec600f9b3bdd253167533959facfefb17b before 92cee08dc4f00e77fd1317e4343c5d458b0abab7; 6.15 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-64037
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-64037
Patch
https://git.kernel.org/stable/c/92cee08dc4f00e77fd1317e4343c5d458b0abab7
Patch
https://git.kernel.org/stable/c/9e360e610a73f62432e986775023d5382773f045
Patch
https://git.kernel.org/stable/c/cbe1c8245e4469d1aa6e12e5d913611376d23788
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