CVE-2021-46999
CriticalCVSS 9.8Exploitation Probability (EPSS)
Elevated risk51th percentile - higher than 51% of all known CVEs
Summary
A vulnerability in the Linux kernel's SCTP protocol leads to a use-after-free of a transport structure. The issue occurs when processing a duplicate COOKIE-ECHO chunk in sctp_sf_do_dupcook_a(), where COOKIE-ACK and SHUTDOWN chunks are allocated with the new association but later used by the old one, potentially causing a system panic.
Risk Assessment
An attacker could exploit this vulnerability to cause a kernel panic, leading to denial of service (DoS). In extreme cases, it might also allow privilege escalation or arbitrary code execution in the kernel.
Recommendation
Immediately update the Linux kernel to a patched version that includes the fix. Monitor distribution security advisories and apply relevant patches promptly.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: sctp: do asoc update earlier in sctp_sf_do_dupcook_a There's a panic that occurs in a few of envs, the call trace is as below: [] general protection fault, ... 0x29acd70f1000a: 0000 [#1] SMP PTI [] RIP: 0010:sctp_ulpevent_notify_peer_addr_change+0x4b/0x1fa [sctp] [] sctp_assoc_control_transport+0x1b9/0x210 [sctp] [] sctp_do_8_2_transport_strike.isra.16+0x15c/0x220 [sctp] [] sctp_cmd_interpreter.isra.21+0x1231/0x1a10 [sctp] [] sctp_do_sm+0xc3/0x2a0 [sctp] [] sctp_generate_timeout_event+0x81/0xf0 [sctp] This is caused by a transport use-after-free issue. When processing a duplicate COOKIE-ECHO chunk in sctp_sf_do_dupcook_a(), both COOKIE-ACK and SHUTDOWN chunks are allocated with the transort from the new asoc. However, later in the sideeffect machine, the old asoc is used to send them out and old asoc's shutdown_last_sent_to is set to the transport that SHUTDOWN chunk attached to in sctp_cmd_setup_t2(), which actually belongs to the new asoc. After the new_asoc is freed and the old asoc T2 timeout, the old asoc's shutdown_last_sent_to that is already freed would be accessed in sctp_sf_t2_timer_expire(). Thanks Alexander and Jere for helping dig into this issue. To fix it, this patch is to do the asoc update first, then allocate the COOKIE-ACK and SHUTDOWN chunks with the 'updated' old asoc. This would make more sense, as a chunk from an asoc shouldn't be sent out with another asoc. We had fixed quite a few issues caused by this.