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CVE-2026-23419
net/rds: Fix circular locking dependency in rds_tcp_tune
Published 2026-04-03 (7 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-2026-23419 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 | fixedDSA-6238-1 · 2026-04-30 · text | 6.12.85-1 | Update the kernel and reboot. DSA-6238-1 shipped the fix on 2026-04-30, in 6.12.85-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.19.8-1 | Update the kernel and reboot. Fixed in 6.19.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.19.8-1 | Update the kernel and reboot. Fixed in 6.19.8-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
syzbot reported a circular locking dependency in rds_tcp_tune() where sk_net_refcnt_upgrade() is called while holding the socket lock: ====================================================== WARNING: possible circular locking dependency detected ====================================================== kworker/u10:8/15040 is trying to acquire lock: ffffffff8e9aaf80 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x4b/0x6f0 but task is already holding lock: ffff88805a3c1ce0 (k-sk_lock-AF_INET6){+.+.}-{0:0}, at: rds_tcp_tune+0xd7/0x930 The issue occurs because sk_net_refcnt_upgrade() performs memory allocation (via get_net_track() -> ref_tracker_alloc()) while the socket lock is held, creating a circular dependency with fs_reclaim. Fix this by moving sk_net_refcnt_upgrade() outside the socket lock critical section. This is safe because the fields modified by the sk_net_refcnt_upgrade() call (sk_net_refcnt, ns_tracker) are not accessed by any concurrent code path at this point. v2: - Corrected fixes tag - check patch line wrap nits - ai commentary nits
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/tcp.c
- What this is
- RDS - RELIABLE DATAGRAM SOCKETSMAINTAINERS section matched on net/rds/ · netdev@vger.kernel.org · Supported
- Kernel module
- rds_tcp
Check it on the machine
grep -wE 'CONFIG_RDS|CONFIG_RDS_TCP' /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 rds_tcpPrints 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, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_RDS, CONFIG_RDS_TCP
- 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
- 2026-04-03 (7 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
- 0.18%, higher than 6.6% 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 |
|---|---|---|
| 5.18 | 6.6.130 | 8babb2714033 |
| 5.18 | 6.12.77 | 8519e6883a94 |
| 5.18 | 6.18.17 | 6ce948fa5459 |
| 5.18 | 6.19.7 | 026bbaeeab9e |
| 5.18 | 7.0 | 6a877ececd6d |
| 5.17.7 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6238-1 | 2026-04-30 | trixie 6.12.85-1 | 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
- RDS/TCP creates a listener on TCP port 16385, and an unauthenticated remote TCP connection reaches rds_tcp_accept_one() and rds_tcp_tune() before protocol-level validation. A local AF_RDS path also exists, but the highest reasonable vector is network.
- AC:LAttack complexity, low
- The attacker can repeatedly trigger the vulnerable lock ordering by opening RDS/TCP connections; no special packet format, credentials, or attacker-uncontrolled race is needed to reach the bad allocation-under-socket-lock path. Applying the higher-severity rule, this is Low complexity.
- PR:NPrivileges required, none
- The network accept path requires no local account, capabilities, or RDS authentication before rds_tcp_tune() is invoked. Remote reachability to the RDS/TCP listener is sufficient in a reasonable affected deployment.
- UI:NUser interaction, none
- No victim user action is required. The attacker can initiate the connection directly.
- S:UScope, unchanged
- The issue affects kernel locking within the same host security authority. It does not cross a VM, container, IOMMU, or other separate security scope boundary.
- C:NConfidentiality impact, none
- The bug is a circular locking dependency involving sk_lock, sk_net_refcnt_upgrade(), ref_tracker allocation, and fs_reclaim. It does not expose kernel memory or create a read primitive.
- I:NIntegrity impact, none
- There is no memory corruption or write primitive; the fix only moves a refcount-tracker allocation outside the socket lock. Integrity is not directly impacted.
- A:HAvailability impact, high
- The lock inversion can lead to a kernel deadlock or system hang, and syzbot reported it as a possible deadlock in the RDS accept worker. Kernel deadlock is High availability impact.