CVE-2026-23125 — linux / linux_kernel
NULL Pointer DereferenceIn the Linux kernel, the following vulnerability has been resolved:
sctp: move SCTP_CMD_ASSOC_SHKEY right after SCTP_CMD_PEER_INIT
A null-ptr-deref was reported in the SCTP transmit path when SCTP-AUTH key initialization fails:
================================================================== KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] CPU: 0 PID: 16 Comm: ksoftirqd/0 Tainted: G W 6.6.0 #2 RIP: 0010:sctp_packet_bundle_auth net/sctp/output.c:264 [inline] RIP: 0010:sctp_packet_append_chunk+0xb36/0x1260 net/sctp/output.c:401 Call Trace:
sctp_packet_transmit_chunk+0x31/0x250 net/sctp/output.c:189 sctp_outq_flush_data+0xa29/0x26d0 net/sctp/outqueue.c:1111 sctp_outq_flush+0xc80/0x1240 net/sctp/outqueue.c:1217 sctp_cmd_interpreter.isra.0+0x19a5/0x62c0 net/sctp/sm_sideeffect.c:1787 sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline] sctp_do_sm+0x1a3/0x670 net/sctp/sm_sideeffect.c:1169 sctp_assoc_bh_rcv+0x33e/0x640 net/sctp/associola.c:1052 sctp_inq_push+0x1dd/0x280 net/sctp/inqueue.c:88 sctp_rcv+0x11ae/0x3100 net/sctp/input.c:243 sctp6_rcv+0x3d/0x60 net/sctp/ipv6.c:1127
The issue is triggered when sctp_auth_asoc_init_active_key() fails in sctp_sf_do_5_1C_ack() while processing an INIT_ACK. In this case, the command sequence is currently:
- SCTP_CMD_PEER_INIT
- SCTP_CMD_TIMER_STOP (T1_INIT)
- SCTP_CMD_TIMER_START (T1_COOKIE)
- SCTP_CMD_NEW_STATE (COOKIE_ECHOED)
- SCTP_CMD_ASSOC_SHKEY
- SCTP_CMD_GEN_COOKIE_ECHO
If SCTP_CMD_ASSOC_SHKEY fails, asoc->shkey remains NULL, while asoc->peer.auth_capable and asoc->peer.peer_chunks have already been set by SCTP_CMD_PEER_INIT. This allows a DATA chunk with auth = 1 and shkey = NULL to be queued by sctp_datamsg_from_user().
Since command interpretation stops on failure, no COOKIE_ECHO should been sent via SCTP_CMD_GEN_COOKIE_ECHO. However, the T1_COOKIE timer has already been started, and it may enqueue a COOKIE_ECHO into the outqueue later. As a result, the DATA chunk can be transmitted together with the COOKIE_ECHO in sctp_outq_flush_data(), leading to the observed issue.
Similar to the other places where it calls sctp_auth_asoc_init_active_key() right after sctp_process_init(), this patch moves the SCTP_CMD_ASSOC_SHKEY immediately after SCTP_CMD_PEER_INIT, before stopping T1_INIT and starting T1_COOKIE. This ensures that if shared key generation fails, authenticated DATA cannot be sent. It also allows the T1_INIT timer to retransmit INIT, giving the client another chance to process INIT_ACK and retry key setup.
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 2.6.24 | 5.10.249 |
| linux / linux_kernel | 5.11 | 5.15.199 |
| linux / linux_kernel | 5.16 | 6.1.162 |
| linux / linux_kernel | 6.2 | 6.6.122 |
| linux / linux_kernel | 6.7 | 6.12.68 |
| linux / linux_kernel | 6.13 | 6.18.8 |
| linux / linux_kernel | 6.19-rc1 | 6.19-rc1.x |
| linux / linux_kernel | 6.19-rc2 | 6.19-rc2.x |
| linux / linux_kernel | 6.19-rc3 | 6.19-rc3.x |
| linux / linux_kernel | 6.19-rc4 | 6.19-rc4.x |
| linux / linux_kernel | 6.19-rc5 | 6.19-rc5.x |
| linux / linux_kernel | 6.19-rc6 | 6.19-rc6.x |
- https://git.kernel.org/stable/c/0c4adb1f391a7b92a0405e9d7c05624c0d9f8a65
- https://git.kernel.org/stable/c/5a309bedf02ee08b0653215f06c94d61ec7a214a
- https://git.kernel.org/stable/c/784428ab1889eb185a1459e9d6bc52df33d572ef
- https://git.kernel.org/stable/c/a80c9d945aef55b23b54838334345f20251dad83
- https://git.kernel.org/stable/c/bf2b543b3cc4ebb4ab5bca4f8dfa5612035d45b8
- https://git.kernel.org/stable/c/e7e81abbcc5620c9532080538f9709a6ea382855
- https://git.kernel.org/stable/c/e94294798548e8cfbd80869e1d2f97efce92582c
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