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CVE-2026-68399
bpf: Fix UAF in sock clone early bailouts
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-2026-68399 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| 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 | 7.1.6-1 | 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. |
The vulnerability
What the bug is
Similar to recent commit 9b51a6155d14 ("bpf,fork: wipe ->bpf_storage before bailouts that access it"), sk_clone() performs an initial shallow copy of the socket field ->sk_bpf_storage via sock_copy() for the cloned socket newsk. If sk_clone() bails out early (e.g. if sk_filter_charge() fails) prior to calling bpf_sk_storage_clone(), newsk->sk_bpf_storage still points to the parent socket's BPF local storage. When newsk is subsequently freed via sk_free(), the deallocation path (__sk_destruct() -> bpf_sk_storage_free()) destroys the parent socket's BPF local storage, leading to a use-after-free (UAF) on the parent socket. Fix this by resetting newsk->sk_bpf_storage to NULL immediately after sock_copy() in sk_clone(), and remove the now redundant initialization from bpf_sk_storage_clone().
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/bpf_sk_storage.c
net/core/sock.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_BPF_SYSCALL /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 builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_BPF_SYSCALL
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
- 7.8 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 2.5% 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 |
|---|---|---|
| 5.2 | 6.18.57 | 01f8a354497b |
| 5.2 | 7.1.6 | 14b49b5ab299 |
| 5.2 | 7.2 | 7cbd0c4cebe4 |
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
- The vulnerable clone path and its early-bailout condition are driven through the BPF sk_storage subsystem and local socket setup (attaching sk_storage, attaching a socket filter, adjusting optmem_max). Per kernel guidance BPF is Local; a remote peer cannot control the bailout conditions.
- AC:LAttack complexity, low
- An attacker who controls the local setup can deterministically force the early bailout by attaching a filter and lowering net.core.optmem_max below the filter size, exactly the sysctl-change scenario the code documents, making sk_filter_charge fail on every clone.
- PR:LPrivileges required, low
- Reaching the bug requires attaching BPF sk_storage and manipulating socket/net settings; these capabilities (CAP_BPF/CAP_NET_ADMIN) can be reachable via user namespaces in some configurations, so the lower-privilege value is chosen per the higher-severity rule.
- UI:NUser interaction, none
- The clone is triggered by connection acceptance or association creation with no victim action; no user interaction is needed.
- S:UScope, unchanged
- The UAF corrupts kernel socket/BPF-storage objects within the kernel's own security authority; no crossing into a separate security scope (no VM/IOMMU boundary).
- C:HConfidentiality impact, high
- The use-after-free lets the attacker reclaim the freed bpf_local_storage object with controlled contents, enabling disclosure of kernel memory; per guidance UAF is High.
- I:HIntegrity impact, high
- UAF on a live socket's BPF storage enables heap grooming and arbitrary-write primitives, giving control-flow hijack potential; per guidance UAF is High.
- A:HAvailability impact, high
- Destroying the parent socket's still-referenced BPF local storage reliably causes memory corruption, oops, and kernel panic; per guidance any UAF/crash is High.