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CVE-2026-64255
wifi: iwlwifi: mld: validate sta_mask before ffs() in BA session handlers
Published 2026-07-24 (3 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64255 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.3-1 | Update the kernel and reboot. Fixed in 7.1.3-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Three BA session handlers use ffs(ba_data->sta_mask) - 1 to derive a station ID without checking that sta_mask is non-zero. When sta_mask is zero, ffs() returns 0 and the subtraction wraps to 0xFFFFFFFF, causing an out-of-bounds access on fw_id_to_link_sta[]. Add WARN_ON_ONCE(!ba_data->sta_mask) guards before each ffs() call, consistent with the existing check in iwl_mld_ampdu_rx_start().
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/net/wireless/intel/iwlwifi/mld/agg.c
- What this is
- INTEL WIRELESS WIFI LINK (iwlwifi)MAINTAINERS section matched on drivers/net/wireless/intel/iwlwifi/ · linux-wireless@vger.kernel.org · Supported
Check it on the machine
grep -wE 'CONFIG_IWLMEI|CONFIG_IWLMLD|CONFIG_IWLWIFI|CONFIG_WLAN|CONFIG_WLAN_VENDOR_INTEL' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian does not build this code in 2 releases. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidn
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_IWLMEI, CONFIG_IWLMLD, CONFIG_IWLWIFI, CONFIG_WLAN, CONFIG_WLAN_VENDOR_INTEL
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-24 (3 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.22%, higher than 12.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.4 | 6.18.38 | 1de92789ce31 |
| 6.4 | 7.1.3 | fe7f339f63c9 |
| 6.4 | 7.2 | f056fc2b9274 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:AAttack vector, adjacent network
- The vulnerable BA-session handlers are driven by Wi-Fi aggregation, BAR/DELBA traffic, firmware notifications, and timers influenced by a radio peer, requiring Wi-Fi adjacency.
- AC:LAttack complexity, low
- A malicious associated MLO peer can control ADDBA parameters, link-state transitions, aggregation traffic, DELBA delivery, and inactivity timing, allowing the sequence to be triggered repeatedly without an uncontrollable race.
- PR:NPrivileges required, none
- The peer must have an existing mac80211 station relationship, but needs no host account, kernel capability, or administrative privilege; a malicious AP or associated station satisfies this gate.
- UI:NUser interaction, none
- Once the wireless relationship exists, the peer can trigger the vulnerable sequence entirely through protocol traffic without further victim action.
- S:UScope, unchanged
- The vulnerable driver and affected kernel memory belong to the same host security authority, with no VM, IOMMU, or other scope boundary crossed.
- C:HConfidentiality impact, high
- The 0xFFFFFFFF index reads a pointer far outside the 16-entry array and then follows it through additional pointer dereferences, permitting disclosure of arbitrary kernel memory under a groomed layout.
- I:HIntegrity impact, high
- A bogus station pointer can reach the PN and mac80211 receive paths, where attacker-controlled PN bytes and station state are written through pointer-derived addresses, potentially enabling kernel memory corruption and control-flow hijacking.
- A:HAvailability impact, high
- The invalid array access or subsequent pointer dereference can fault in NAPI, RX-queue, or timer context, causing a kernel oops or panic and complete system denial of service.