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CVE-2026-98130
sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START
Published 2026-09-25 (24 days ago) by the Linux kernel CNA. Subsystem net/sctp. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-98130 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-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.7-1 | Update the kernel and reboot. Fixed in 7.2.7-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.7-1 | Update the kernel and reboot. Fixed in 7.2.7-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The SCTP_CMD_TIMER_START handler checks timer_pending() before calling timer_reduce(). The timer can expire and detach between these operations, causing timer_reduce() to rearm the timer without taking the association reference required for the newly armed timer. The timer callback later unconditionally drops its association reference, which can leave the association reference count unbalanced and result in use-after-free during association teardown. Use the return value of timer_reduce() to determine whether the timer was actually armed. Take the association reference only when timer_reduce() successfully starts a new timer, closing the race between checking the timer state and rearming it. This issue was reported by Nico Yip (@_cyeaa_) working with TrendAI Zero Day Initiative.
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/sctp/sm_sideeffect.c
- What this is
- SCTP PROTOCOLMAINTAINERS section matched on net/sctp/ · linux-sctp@vger.kernel.org · Maintained
- Kernel module
- sctp
Check it on the machine
grep -w CONFIG_IP_SCTP /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 sctpPrints 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_IP_SCTP
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
- 2026-09-25 (24 days ago)source
- CVSS
- 8.1 high
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.58%, higher than 46.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/sctp
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.7 | 5.10.271 | cbf2df9aac42 |
| 5.7 | 5.15.222 | 3205a20f837f |
| 5.7 | 6.1.189 | 755d70ca845f |
| 5.7 | 6.6.158 | 09e7f9290d63 |
| 5.7 | 6.12.111 | e42ba56281ca |
| 5.7 | 6.18.53 | 00b841bac102 |
| 5.7 | 7.2.7 | 3d698d1e6c8b |
| 5.7 | 7.3 | 2188569e7e1b |
| 4.19.126 | 0 | 0 |
| 5.4.44 | 0 | 0 |
| 5.6.16 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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
- A remote SCTP peer's restart COOKIE-ECHO goes through sctp_sf_do_5_2_4_dupcook()/sctp_sf_do_dupcook_a() in SHUTDOWN_SENT and on to sctp_sf_do_9_2_start_shutdown(). That queues SCTP_CMD_TIMER_START for T2-shutdown while T2 is already armed, which reaches the racy timer_pending()/timer_reduce() pair in sctp_cmd_interpreter(). SCTP runs over routable IP.
- AC:HAttack complexity, high
- The peer must time its COOKIE-ECHO so that T2 expires on another CPU in the window between timer_pending() and timer_reduce(), which is two adjacent statements. The attacker can retry by timing packets around T2 retransmissions, but cannot control when the kernel timer fires relative to softirq processing. The target association must also be in SHUTDOWN_SENT with its socket closing.
- PR:NPrivileges required, none
- SCTP association setup and the restart COOKIE-ECHO path in sctp_sf_do_dupcook_a() need no authentication. The attacker is just the unauthenticated peer of the association.
- UI:NUser interaction, none
- No victim action is needed beyond the SCTP service normally closing an association, which puts it in SHUTDOWN_SENT. The attacker sends all the triggering packets.
- S:UScope, unchanged
- The corruption is confined to the kernel's own sctp_association object. No security boundary such as a VM or IOMMU is crossed.
- C:HConfidentiality impact, high
- Re-arming the timer without sctp_association_hold() lets sctp_generate_timeout_event() call sctp_association_put() one time too many. The association is then freed while still referenced, a use-after-free of a large slab object whose reclaimed contents can be used to leak kernel memory.
- I:HIntegrity impact, high
- The freed sctp_association holds function-relevant state such as timers, transports and the outqueue. Later timer callbacks and teardown writes into reclaimed memory give a write primitive that could be used to hijack control flow.
- A:HAvailability impact, high
- The unbalanced refcount causes a refcount underflow or use-after-free during association teardown or a later timer callback, crashing the kernel.