CVE-2026-23125
Unknown Unknown - Not Provided
Null Pointer Dereference in Linux Kernel SCTP Transmit Path

Publication date: 2026-02-14

Last updated on: 2026-03-18

Assigner: kernel.org

Description
In 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.
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Meta Information
Published
2026-02-14
Last Modified
2026-03-18
Generated
2026-06-16
AI Q&A
2026-02-14
EPSS Evaluated
2026-06-15
NVD
CVE-2026-23125
EUVD
EUVD-2026-5911
Affected Vendors & Products
Showing 12 associated CPEs
Vendor Product Version / Range
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 5.11 (inc) to 5.15.199 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.162 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.122 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.68 (exc)
linux linux_kernel From 6.13 (inc) to 6.18.8 (exc)
linux linux_kernel 6.19
linux linux_kernel From 2.6.24 (inc) to 5.10.249 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-476 The product dereferences a pointer that it expects to be valid but is NULL.
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Executive Summary

This vulnerability exists in the Linux kernel's SCTP (Stream Control Transmission Protocol) transmit path. It is caused by a null pointer dereference that occurs when the SCTP-AUTH key initialization fails during the processing of an INIT_ACK message.

Specifically, if the command SCTP_CMD_ASSOC_SHKEY fails, the shared key (shkey) remains NULL, but the peer's authentication capability and peer chunks are already set. This allows an authenticated DATA chunk with auth = 1 but a NULL shared key to be queued and transmitted.

Because the command sequence stops on failure, no COOKIE_ECHO should be sent, but the timer T1_COOKIE may still enqueue a COOKIE_ECHO later. This causes the DATA chunk to be transmitted together with the COOKIE_ECHO, leading to a null pointer dereference and potential kernel crash.

The fix moves the SCTP_CMD_ASSOC_SHKEY command earlier in the sequence to ensure that if shared key generation fails, authenticated DATA cannot be sent, preventing the issue.

Impact Analysis

This vulnerability can cause a null pointer dereference in the Linux kernel, which may lead to a kernel crash or system instability.

If exploited, it could disrupt network communications using SCTP by causing denial of service conditions on affected systems.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

The vulnerability has been resolved by moving the SCTP_CMD_ASSOC_SHKEY command immediately after SCTP_CMD_PEER_INIT in the Linux kernel SCTP implementation. This change ensures that if shared key generation fails, authenticated DATA cannot be sent, preventing the null pointer dereference.

Therefore, the immediate mitigation step is to update your Linux kernel to a version that includes this fix (version 6.6.0 or later with the patch applied).

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