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CVE-2026-53075
ppp: require CAP_NET_ADMIN in target netns for unattached ioctls
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53075 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
/dev/ppp open is currently authorized against file->f_cred->user_ns, while unattached administrative ioctls operate on current->nsproxy->net_ns. As a result, a local unprivileged user can create a new user namespace with CLONE_NEWUSER, gain CAP_NET_ADMIN only in that new user namespace, and still issue PPPIOCNEWUNIT, PPPIOCATTACH, or PPPIOCATTCHAN against an inherited network namespace. Require CAP_NET_ADMIN in the user namespace that owns the target network namespace before handling unattached PPP administrative ioctls. This preserves normal pppd operation in the network namespace it is actually privileged in, while rejecting the userns-only inherited-netns case.
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/ppp/ppp_generic.c
- What this is
- PPP PROTOCOL DRIVERS AND COMPRESSORSMAINTAINERS section matched on drivers/net/ppp/ppp_* · linux-ppp@vger.kernel.org · Orphan
- Kernel module
- ppp_generic
Check it on the machine
grep -wE 'CONFIG_PPP|CONFIG_PPPOE|CONFIG_PPPOL2TP|CONFIG_PPP_ASYNC|CONFIG_PPP_BSDCOMP|CONFIG_PPP_DEFLATE|CONFIG_PPP_MPPE|CONFIG_PPP_SYNC_TTY|CONFIG_PPTP' /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 ppp_genericPrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_PPP, CONFIG_PPPOE, CONFIG_PPPOL2TP, CONFIG_PPP_ASYNC, CONFIG_PPP_BSDCOMP, CONFIG_PPP_DEFLATE, CONFIG_PPP_MPPE, CONFIG_PPP_SYNC_TTY, CONFIG_PPTP
- 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
- 2026-06-24 (4 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.25%, higher than 15.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- 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 |
|---|---|---|
| 2.6.30 | 5.10.258 | c9edd90c57ae |
| 2.6.30 | 5.15.209 | 5080e188c914 |
| 2.6.30 | 6.1.175 | 67e901e28d17 |
| 2.6.30 | 6.6.141 | 954745d0223e |
| 2.6.30 | 6.12.91 | 3b2c2157dc2a |
| 2.6.30 | 6.18.33 | 5013be175c7f |
| 2.6.30 | 7.0.10 | 1a8a51ce8507 |
| 2.6.30 | 7.1 | 2bb6379416fd |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | 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
- The vulnerable PPP administrative ioctls are reached locally through `/dev/ppp` and the `ioctl` syscall, not by remote packets.
- AC:LAttack complexity, low
- An attacker can deterministically create a user namespace, open `/dev/ppp`, and issue the unattached ioctls against the inherited target network namespace; no race or external condition is required.
- PR:LPrivileges required, low
- A basic unprivileged local user can gain `CAP_NET_ADMIN` only inside a new user namespace and abuse the pre-fix check, so this does not require real root or host `CAP_NET_ADMIN`.
- UI:NUser interaction, none
- No victim action is required after the attacker has local code execution; the attacker directly invokes the namespace and ioctl operations.
- S:CScope, changed
- The bug crosses the user-namespace capability boundary by allowing capabilities in one user namespace to administer PPP resources in a network namespace owned by another user namespace.
- C:HConfidentiality impact, high
- By attaching to existing PPP units or channels, an attacker can read PPP control/authentication traffic and can plausibly expose sensitive PPP-session data in affected deployments.
- I:HIntegrity impact, high
- The attacker can create PPP interfaces, attach to units/channels, alter PPP parameters, and inject or redirect PPP frames in a network namespace they should not administer.
- A:HAvailability impact, high
- The attacker can disrupt PPP connectivity by changing interface/channel state, disconnecting or bridging channels, or exhausting PPP resources, causing loss of network availability in PPP-dependent systems.