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CVE-2026-68335
rds: drop incoming messages that cross network namespace boundaries
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem net/rds. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68335 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 | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. 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-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
rds_find_bound() looks up the destination socket using a global rhashtable keyed solely on (addr, port, scope_id). Network namespaces are not part of the key, so a sender in netns A can deliver an incoming message (inc) to a socket that lives in a different netns B. When this happens, inc->i_conn points to an rds_connection whose c_net is netns A, but the receiving rs lives in netns B. Once the child process that created netns A exits, cleanup_net() calls rds_loop_exit_net() -> rds_loop_kill_conns() -> rds_conn_destroy(), freeing that connection. If the survivor socket in netns B still holds the inc, any subsequent dereference of inc->i_conn is a use-after-free. There are two dangerous sites in rds_clear_recv_queue(): 1. inc->i_conn->c_lcong (offset 88 of freed rds_connection, size 200) read via rds_recv_rcvbuf_delta() -- confirmed by KASAN. 2. inc->i_conn->c_trans->inc_free(inc) (function pointer at offset 80) called via rds_inc_put() when the inc refcount reaches zero -- same race window, potential call-through-freed-object primitive. The bug is reachable from unprivileged user namespaces (CLONE_NEWUSER + CLONE_NEWNET), available since Linux 3.8. Fix this by rejecting the delivery in rds_recv_incoming() when the socket returned by rds_find_bound() belongs to a different network namespace than the connection that carried the message. Use the existing rds_conn_net() / sock_net() helpers and net_eq() for the comparison.
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/rds/recv.c
- What this is
- RDS - RELIABLE DATAGRAM SOCKETSMAINTAINERS section matched on net/rds/ · netdev@vger.kernel.org · Supported
- Kernel module
- rds
Check it on the machine
grep -w CONFIG_RDS /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 rdsPrints 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_RDS
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
- 0.14%, higher than 2.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/rds
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.18 | 5.10.265 | 742ff6f02545 |
| 4.18 | 5.15.216 | abff41fd9283 |
| 4.18 | 6.1.183 | 03c574112e5d |
| 4.18 | 6.6.148 | 1e2e2d980694 |
| 4.18 | 6.12.101 | cfb3ce07b705 |
| 4.18 | 6.18.42 | 959104253314 |
| 4.18 | 7.1.6 | 0f8690e38691 |
| 4.18 | 7.2 | 5521ae71e32a |
| 4.17.19 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | 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 syscall access: the attacker must create RDS sockets and a network namespace (CLONE_NEWUSER|CLONE_NEWNET), then trigger namespace teardown to free the connection. A remote RDS peer cannot drive the netns-destruction half of the sequence, so the vulnerability is reachable only locally.
- AC:LAttack complexity, low
- The attacker controls the entire sequence deterministically — bind a socket in one netns, send a loopback RDS message from a second netns so the inc is queued cross-netns, then exit that netns to free inc->i_conn. No race must be won and no uncontrollable precondition exists; the UAF is confirmed reproducible under KASAN.
- PR:LPrivileges required, low
- Only an unprivileged local user account is required; the needed CAP_NET_ADMIN for creating and configuring the second network namespace is obtained inside a user namespace the attacker owns, as the commit explicitly notes ("reachable from unprivileged user namespaces").
- UI:NUser interaction, none
- The attacker performs every step — socket creation, cross-netns send, namespace teardown, and the subsequent read/close that dereferences the freed connection — with no action from any other user or administrator.
- S:UScope, unchanged
- The use-after-free corrupts kernel memory within the same kernel security authority; there is no crossing of a hypervisor, IOMMU, or comparable trust boundary.
- C:HConfidentiality impact, high
- The stale inc->i_conn is dereferenced to read c_lcong from a freed 200-byte rds_connection, and the freed slot can be reclaimed with attacker-groomed data, giving a use-after-free read primitive usable to disclose kernel memory contents.
- I:HIntegrity impact, high
- rds_inc_put() calls inc->i_conn->c_trans->inc_free(inc) through a function pointer at offset 80 of the freed object — an indirect call through freed memory that the commit calls a "call-through-freed-object primitive", which after heap reclamation is a control-flow hijack path leading to arbitrary kernel modification.
- A:HAvailability impact, high
- Dereferencing the freed rds_connection in rds_clear_recv_queue() and calling through its freed transport vtable reliably corrupts kernel state and panics the machine (KASAN-confirmed use-after-free), causing a full denial of service.