CVE-2026-52924
Received Received - Intake
Use-After-Free in Linux Kernel SCTP Implementation

Publication date: 2026-06-24

Last updated on: 2026-06-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: sctp: purge outqueue on stale COOKIE-ECHO handling sctp_stream_update() is only invoked when the association is moved into COOKIE_WAIT during association setup/reconfiguration. In this path, the outbound stream scheduler state (stream->out_curr) is expected to be clean, since no user data should have been transmitted yet unless the state machine has already partially progressed. However, a corner case exists in sctp_sf_do_5_2_6_stale(): when a Stale Cookie ERROR is received, the association is rolled back from COOKIE_ECHOED to COOKIE_WAIT. In this scenario, user data may already have been queued and even bundled with the COOKIE-ECHO chunk. During the rollback, sctp_stream_update() frees the old stream table and installs a new one, but it does not invalidate stream->out_curr. As a result, out_curr may still point to a freed sctp_stream_out entry from the previous stream state. Later, SCTP scheduler dequeue paths (FCFS, RR, PRIO, etc.) rely on stream->out_curr->ext, which can lead to use-after-free once the old stream state has been released via sctp_stream_free(). This results in crashes such as (reported by Yuqi): BUG: KASAN: slab-use-after-free in sctp_sched_fcfs_dequeue+0x13a/0x140 Read of size 8 at addr ff1100004d4d3208 by task mini_poc/9312 CPU: 1 UID: 1001 PID: 9312 Comm: mini_poc Not tainted 7.1.0-rc1-00305-gbd3a4795d574 #5 PREEMPT(full) sctp_sched_fcfs_dequeue+0x13a/0x140 sctp_outq_flush+0x1603/0x33e0 sctp_do_sm+0x31c9/0x5d30 sctp_assoc_bh_rcv+0x392/0x6f0 sctp_inq_push+0x1db/0x270 sctp_rcv+0x138d/0x3c10 Fix this by fully purging the association outqueue when handling the Stale Cookie case. This ensures all pending transmit and retransmit state is dropped, and any scheduler cached pointers are invalidated, making it safe to rebuild stream state during COOKIE_WAIT restart. Updating only stream->out_curr would be insufficient, since queued and retransmittable data would still reference the old stream state and trigger later use-after-free in dequeue paths.
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Meta Information
Published
2026-06-24
Last Modified
2026-06-24
Generated
2026-06-24
AI Q&A
2026-06-24
EPSS Evaluated
N/A
NVD
CVE-2026-52924
EUVD
EUVD-2026-38727
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 7.1.0-rc1-00305
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Exploitability
CWE
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability exists in the Linux kernel's SCTP (Stream Control Transmission Protocol) implementation. It occurs during the handling of a stale COOKIE-ECHO message, where the association state is rolled back from COOKIE_ECHOED to COOKIE_WAIT. In this rollback, user data that was already queued may still reference old stream state that has been freed. Specifically, the outbound stream scheduler state pointer (out_curr) can point to freed memory, leading to a use-after-free condition.

This use-after-free can cause kernel crashes when the SCTP scheduler tries to dequeue data using the invalid pointer. The fix involves fully purging the association's outqueue during stale COOKIE handling to drop all pending transmit and retransmit data and invalidate cached scheduler pointers, preventing access to freed memory.

Impact Analysis

This vulnerability can lead to kernel crashes due to use-after-free errors in the SCTP scheduler. Such crashes can cause denial of service (DoS) conditions on affected systems, potentially disrupting network communications that rely on SCTP.

Mitigation Strategies

The vulnerability has been resolved by updating the Linux kernel to fully purge the association outqueue when handling the Stale Cookie case. This ensures that all pending transmit and retransmit state is dropped and any scheduler cached pointers are invalidated, preventing use-after-free errors.

Therefore, the immediate step to mitigate this vulnerability is to update your Linux kernel to a version that includes this fix.

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