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CVE-2026-89477
sctp: fix NULL deref on untransmitted RECONF completion
Published 2026-09-11 (37 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-2026-89477 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 | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. 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
sctp_process_strreset_outreq(), sctp_process_strreset_addstrm_out() and sctp_process_strreset_resp() complete a pending stream reconfiguration request by stopping the reconf timer on the transport it was sent on: t = asoc->strreset_chunk->transport; if (timer_delete(&t->reconf_timer)) sctp_transport_put(t); chunk->transport is assigned by __sctp_packet_append_chunk() when the chunk is appended to an outbound packet, and sctp_outq_flush_ctrl() arms the reconf timer at that same point. A request already published in asoc->strreset_chunk but not yet transmitted has neither, so completing it dereferences NULL. Two ways to get there. sctp_send_asconf_del_ip() sets asoc->src_out_of_asoc_ok without sending anything when the address being removed is the association's last one, and sctp_outq_flush_ctrl() then leaves every non-ASCONF control chunk queued; as only sctp_process_asconf_ack() clears that flag, it persists. An unprivileged process that removes such an address and then asks for a stream reset panics the kernel from softirq. A peer needs neither ASCONF nor local help: sctp_cmd_interpreter() uncorks the outqueue only once the whole packet has been processed, so a reply built while walking a RECONF chunk stays untransmitted for the rest of that walk, and one RECONF chunk carrying [Incoming SSN Reset Request, Outgoing SSN Reset Request, Response] -- or two RECONF chunks in one packet -- reaches the same dereference. KASAN: null-ptr-deref in range [0x00000000000001e8-0x00000000000001ef] RIP: 0010:timer_delete+0x67/0x110 Call Trace: <IRQ> sctp_process_strreset_addstrm_out (net/sctp/stream.c:832) sctp_sf_do_reconf (net/sctp/sm_statefuns.c:4212) sctp_do_sm (net/sctp/sm_sideeffect.c:1172) sctp_assoc_bh_rcv (net/sctp/associola.c:1044) sctp_rcv (net/sctp/input.c:243) ip_local_deliver (net/ipv4/ip_input.c:262) process_backlog (net/core/dev.c:6680) </IRQ> A response can only acknowledge a request that was actually sent, so do not match asoc->strreset_chunk while chunk->transport is NULL. Guarding the lookup covers all three completion sites.
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/stream.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
- 2026-09-11 (37 days 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
- 0.50%, higher than 41.6% 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 |
|---|---|---|
| 4.11 | 5.10.270 | 79ff751311e8 |
| 4.11 | 5.15.221 | 53141db97968 |
| 4.11 | 6.1.188 | 68891125af5a |
| 4.11 | 6.6.157 | b2d6d873b4df |
| 4.11 | 6.12.109 | 77ea60f2d240 |
| 4.11 | 6.18.50 | 25419f516ea8 |
| 4.11 | 7.2.4 | 0ee697defc05 |
| 4.11 | 7.3 | 2db9bfa3e27b |
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 reaches the bug via sctp_rcv() -> sctp_assoc_bh_rcv() -> sctp_sf_do_reconf() on an established association; one RECONF carrying Incoming/Outgoing SSN Reset plus Response, or two bundled RECONF chunks, completes an untransmitted strreset_chunk. This is internet-facing SCTP (telecom/Diameter), not a local-only syscall.
- AC:LAttack complexity, low
- The attacker fully controls the packet: sctp_cmd_interpreter() keeps the outqueue corked until the whole packet is processed, so the generated RECONF reply stays untransmitted and the follow-on parameter/chunk deterministically NULL-dereferences. request_seq is the peer's initial TSN from INIT/INIT-ACK; no race or uninfluenceable memory layout is required.
- PR:NPrivileges required, none
- Triggering requires only a network-reachable established SCTP association; the attacker needs no local account, capabilities, or namespaces on the victim. RECONF is processed in ESTABLISHED without SCTP-AUTH by default (empty auth chunk list), so no extra credentials beyond being the SCTP peer.
- UI:NUser interaction, none
- Exploitation is driven entirely by inbound SCTP packets processed automatically in softirq on a listening or already-associated endpoint; no victim user action such as opening a file or mounting a filesystem is required.
- S:UScope, unchanged
- Impact is a kernel NULL dereference and oops in the host SCTP stack, remaining in the same kernel security authority; it is not a VM/guest-to-host escape, IOMMU bypass, or other cross-boundary breakout.
- C:NConfidentiality impact, none
- The defect is a pure NULL pointer dereference of strreset_chunk->transport in timer_delete() (KASAN range around offset 0x1e8). No out-of-bounds read, UAF object reuse, or other disclosure primitive is involved.
- I:NIntegrity impact, none
- Only a NULL transport pointer is loaded and passed to timer_delete(); there is no write, type confusion, or memory corruption that could hijack control flow or modify kernel state beyond the crash.
- A:HAvailability impact, high
- timer_delete() on the NULL transport oopses/panics the kernel from SCTP receive softirq (documented KASAN null-ptr-deref in sctp_process_strreset_*), which is a full availability loss and can be repeated at will by the peer.