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CVE-2026-68287
drop_monitor: fix size calculations for 64-bit attributes
Published 2026-08-10 (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-2026-68287 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-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
net_dm_packet_report_fill() and net_dm_hw_packet_report_fill() use nla_put_u64_64bit() to append 64-bit attributes (NET_DM_ATTR_PC and NET_DM_ATTR_TIMESTAMP). On 32-bit architectures without CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, nla_put_u64_64bit() may append a 4-byte NET_DM_ATTR_PAD attribute for 64-bit alignment. However, net_dm_packet_report_size() and net_dm_hw_packet_report_size() used nla_total_size(sizeof(u64)) instead of nla_total_size_64bit(sizeof(u64)), budgeting 12 bytes instead of up to 16 bytes. This under-estimation of SKB size can lead to an skb_over_panic() when __nla_reserve() or skb_put() is subsequently called. Fix this by using nla_total_size_64bit(sizeof(u64)) in both size calculations.
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/drop_monitor.c
- What this is
- NETWORK DROP MONITORMAINTAINERS section matched on net/core/drop_monitor.c · netdev@vger.kernel.org · Maintained
- Kernel module
- drop_monitor
Check it on the machine
grep -w CONFIG_NET_DROP_MONITOR /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 drop_monitorPrints 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_DROP_MONITOR
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
- 2026-08-10 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.68%, higher than 51.3% 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 |
|---|---|---|
| 5.4 | 6.1.189 | 1275a4769c12 |
| 5.4 | 6.6.158 | 0da8f531336b |
| 5.4 | 6.12.111 | 6048ed2dfb33 |
| 5.4 | 6.18.53 | 925669d4cfd4 |
| 5.4 | 7.1.6 | 4a9e30764e80 |
| 5.4 | 7.2 | 7089f7ab99c8 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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:NAttack vector, network
- The report path runs in net/core/drop_monitor.c whenever a received packet is dropped or hardware-trapped; a remote unauthenticated attacker triggers it simply by sending packets that get dropped, and controls skb->len which feeds payload_len and thus the under-sized allocation.
- AC:LAttack complexity, low
- On an affected build the attacker can drive the path at will, tuning packet length byte-by-byte to land the under-budgeted skb exactly at an allocator bucket boundary; no race or unpredictable state is involved.
- PR:NPrivileges required, none
- Enabling packet-alert mode is the victim administrator's monitoring configuration; the attacker's own action is only sending packets that get dropped, which needs no account, credentials or privileges on the target.
- UI:NUser interaction, none
- The drop-report path is executed automatically by the kernel workqueue when packets are dropped; no local user action is needed.
- S:UScope, unchanged
- The under-allocated skb and the resulting skb_over_panic() are entirely within the kernel's own security authority; no VM, IOMMU or sandbox boundary is crossed.
- C:NConfidentiality impact, none
- __nla_reserve() detects the overrun in skb_put() and panics before any data is written or read past the buffer, so no memory contents are disclosed to the attacker.
- I:NIntegrity impact, none
- skb_over_panic() aborts before the out-of-bounds payload copy occurs, so no adjacent memory is modified and no control-flow primitive is obtained.
- A:HAvailability impact, high
- The size under-estimation makes skb_put() exceed skb->end, invoking skb_over_panic() which calls BUG() and takes down the machine, a complete and repeatable denial of service.