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CVE-2021-46999

Disclosure Date: February 28, 2024 •
CVE-2021-46999
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

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.

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CVSS V3 Severity and Metrics
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General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
Linux d624f2991b97
Linux b1b31948c0af
Linux f01988ecf365
Linux not down converted
Prerequisites
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Discovered By
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Metasploit Module
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Vendors

  • Linux

Products

  • Linux
Technical Analysis