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CVE-2026-68341
ovpn: fix use after free in unlock_ovpn()
Published 2026-08-10 (2 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-2026-68341 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 | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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
unlock_ovpn() iterates over the release_list using llist_for_each_entry() and drops the peer reference inside the loop body via ovpn_peer_put(). If this drops the last reference, the peer is eventually freed. However, llist_for_each_entry() reads peer->release_entry.next in the loop advance expression, which runs after the body. By that time the peer may have already been freed, resulting in a use after free when advancing to the next list entry. Fix this by using llist_for_each_entry_safe(), which caches the next pointer before executing the loop body.
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/ovpn/peer.c
- What this is
- OPENVPN DATA CHANNEL OFFLOADMAINTAINERS section matched on drivers/net/ovpn/ · openvpn-devel@lists.sourceforge.net · Supported
- Kernel module
- ovpn
Check it on the machine
grep -w CONFIG_OVPN /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 ovpnPrints 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 with an answer 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. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidm
- ?
- not established - no Makefile entry for the affected file
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
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 switch
- CONFIG_OVPN
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
- 8.8 high
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.57%, higher than 45.8% 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 |
|---|---|---|
| 6.16 | 6.18.42 | 5b96227c0e8b |
| 6.16 | 7.1.6 | 4cdb209f12a8 |
| 6.16 | 7.2 | e1ad6fe5db71 |
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
- unlock_ovpn() is reached directly from remote-peer activity: a malformed/aborted OpenVPN TCP stream schedules ovpn_tcp_peer_del_work() -> ovpn_peer_del() (tcp.c:154/287/506), peer disconnect hits ovpn_tcp_close(), and remote peers falling silent make ovpn_peer_keepalive_work() queue peers onto release_list. No local action is needed to enter the vulnerable loop.
- AC:LAttack complexity, low
- The attacker controls both the trigger and its repetition rate: a remote peer can force transport errors, reconnects and keepalive expiries arbitrarily often, and in MP mode can control how many peers land on release_list at once, plus generate traffic-driven allocation pressure to influence slab reuse of the freed ovpn_peer.
- PR:LPrivileges required, low
- The vulnerable loop only runs for peers already installed in the kernel, which the openvpn userspace daemon does for a connected client, so the attacker acts as an established (low-privileged) VPN peer rather than an unauthenticated stranger; no administrative rights on the target are needed.
- UI:NUser interaction, none
- Peer removal and the subsequent list walk happen automatically inside the kernel's TCP error/close handling and keepalive worker; no administrator or user action on the victim host is required.
- S:UScope, unchanged
- The use-after-free corrupts kernel heap state within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- The freed ovpn_peer is re-read to obtain the next list pointer, so a reclaimed and re-populated slab object lets the attacker steer the walk onto arbitrary memory that is then dereferenced (peer->sock, peer->refcount), yielding a kernel-memory read primitive and disclosure of sensitive kernel data.
- I:HIntegrity impact, high
- Continuing the walk onto a stale/attacker-groomed object causes rcu_replace_pointer() writes, lock_sock() and kref_put() (a controlled decrement plus invocation of a release callback) on a bogus struct ovpn_peer, giving heap-spray-based write and control-flow-hijack potential typical of exploitable UAFs.
- A:HAvailability impact, high
- Dereferencing freed or recycled memory as an ovpn_peer reliably produces oops/panic or slab corruption, taking down the VPN gateway kernel; the path is remotely repeatable, so it is a dependable denial of service.