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CVE-2026-74479
net: pktgen: fix proc entry use-after-free
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/core. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74479 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
pktgen_change_name() replaces pkt_dev->entry while holding t->if_lock. pktgen_remove_device() removes the same entry before _rem_dev_from_if_list() takes that lock. This allows the following interleaving: CPU 0 (NETDEV_CHANGENAME) CPU 1 (kpktgend) if_lock(t) proc_remove(pkt_dev->entry) proc_remove(pkt_dev->entry) pkt_dev->entry = proc_create_data(...) if_unlock(t) The kthread can pass the stale proc_dir_entry to proc_remove() after the rename path has freed it. A reproducer with a widened race window reports: BUG: KASAN: slab-use-after-free in proc_remove+0x78/0x80 Read of size 8 at addr ffff8881478fea70 by task kpktgend_0/67 Call Trace: proc_remove+0x78/0x80 pktgen_remove_device.isra.0+0x11c/0x4c0 pktgen_thread_worker+0x1214/0x6bc0 kthread+0x2c6/0x3b0 Allocated by task 95: __proc_create+0x204/0x790 proc_create_data+0x72/0xe0 pktgen_thread_write+0xd61/0x1510 Freed by task 28: kmem_cache_free+0xcb/0x3d0 proc_free_inode+0x5b/0x80 rcu_core+0x50a/0x1850 The buggy address belongs to the object at ffff8881478fea00 which belongs to the cache proc_dir_entry of size 192 Move proc_remove() into the if_lock-protected list removal helper. Keep it before list_del_rcu() to preserve the ordering required by add_device(). The rename path must then finish replacing the entry before removal, or it observes that the device is no longer on the list.
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.
net/core/pktgen.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
- Kernel module
- pktgen
Check it on the machine
grep -w CONFIG_NET_PKTGEN /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.
lsmod | grep -w pktgenPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_NET_PKTGEN
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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/core
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.22 | 5.10.266 | 82ed3db9269c |
| 2.6.22 | 5.15.217 | d1cc9797cf8f |
| 2.6.22 | 6.1.184 | 7991c7cff8b8 |
| 2.6.22 | 6.6.153 | 577443530cb5 |
| 2.6.22 | 6.12.105 | f85a58340b91 |
| 2.6.22 | 6.18.44 | 4ef801b838d8 |
| 2.6.22 | 7.1.8 | b006a5404470 |
| 2.6.22 | 7.2 | 817ff6efdb7f |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
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:LAttack vector, local
- Exploitation requires local access to /proc/net/pktgen procfs writes and a SIOCSIFNAME/ip-link rename of a pktgen-bound netdev; pktgen is configured only via local proc and ioctl paths, not via remote network packets.
- AC:LAttack complexity, low
- The UAF is a race between pktgen_change_name() on NETDEV_CHANGENAME and pktgen_remove_device() in kpktgend; an attacker controls both sides concurrently via rem_device_all/unregister and interface rename, so success does not depend on uncontrollable timing.
- PR:LPrivileges required, low
- Triggering rename needs ns_capable(CAP_NET_ADMIN) and pktgen proc writes are mode 0600; CAP_NET_ADMIN is obtainable by an unprivileged user via user/network namespaces (unshare -Urn), so real init-namespace root is not required.
- UI:NUser interaction, none
- No victim interaction is required; the attacker drives pktgen device add/remove and netdev rename/unregister directly through local proc writes and netlink/ioctl without needing another user to act.
- S:UScope, unchanged
- Impact is kernel slab corruption and potential privilege escalation within the same kernel security domain; it does not inherently cross VM, container, or IOMMU boundaries without additional unrelated primitives.
- C:HConfidentiality impact, high
- The bug is a slab use-after-free of a proc_dir_entry in proc_remove(); KASAN shows reads of freed 192-byte objects, and UAF on proc metadata can be turned into arbitrary kernel memory disclosure via heap grooming.
- I:HIntegrity impact, high
- Corrupting or reusing the freed proc_dir_entry during proc_remove()/procfs teardown can enable attacker-controlled writes and control-flow hijack in kernel context, not merely a benign NULL dereference crash.
- A:HAvailability impact, high
- Concurrent rename and removal causes proc_remove() to dereference a freed proc_dir_entry, producing KASAN slab-use-after-free and kernel oops/panic; even without full exploit development, the UAF reliably threatens system availability.