In the Linux kernel, the following vulnerability has been resolved:
sctp: detect and prevent references to a freed transport in sendmsg
sctp_sendmsg() re-uses associations and transports when possible by doing a lookup based on the socket endpoint and the message destination address, and then sctp_sendmsg_to_asoc() sets the selected transport in all the message chunks to be sent.
There's a possible race condition if another thread triggers the removal of that selected transport, for instance, by explicitly unbinding an address with setsockopt(SCTP_SOCKOPT_BINDX_REM), after the chunks have been set up and before the message is sent. This can happen if the send buffer is full, during the period when the sender thread temporarily releases the socket lock in sctp_wait_for_sndbuf().
This causes the access to the transport data in sctp_outq_select_transport(), when the association outqueue is flushed, to result in a use-after-free read.
This change avoids this scenario by having sctp_transport_free() signal the freeing of the transport, tagging it as "dead". In order to do this, the patch restores the "dead" bit in struct sctp_transport, which was removed in commit 47faa1e4c50e ("sctp: remove the dead field of sctp_transport").
Then, in the scenario where the sender thread has released the socket lock in sctp_wait_for_sndbuf(), the bit is checked again after re-acquiring the socket lock to detect the deletion. This is done while holding a reference to the transport to prevent it from being freed in the process.
If the transport was deleted while the socket lock was relinquished, sctp_sendmsg_to_asoc() will return -EAGAIN to let userspace retry the send.
The bug was found by a private syzbot instance (see the error report [1] and the C reproducer that triggers it [2]).
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 3.18.128 | 3.19 |
| linux / linux_kernel | 4.4.166 | 4.5 |
| linux / linux_kernel | 4.9.142 | 4.10 |
| linux / linux_kernel | 4.14.85 | 4.15 |
| linux / linux_kernel | 4.19.6 | 5.4.293 |
| linux / linux_kernel | 5.5 | 5.10.237 |
| linux / linux_kernel | 5.11 | 5.15.181 |
| linux / linux_kernel | 5.16 | 6.1.135 |
| linux / linux_kernel | 6.2 | 6.6.88 |
| linux / linux_kernel | 6.7 | 6.12.24 |
| linux / linux_kernel | 6.13 | 6.13.12 |
| linux / linux_kernel | 6.14 | 6.14.3 |
| linux / linux_kernel | 6.15-rc1 | 6.15-rc1.x |
| debian / debian_linux | 11.0 | 11.0.x |
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
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Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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