# CVE-2021-47591: linux: In the Linux kernel, the following vulnerability has been resolved:  mptcp: remove tcp ulp setsockopt support  TCP_UL...

CVE-2021-47591 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47591, released June 19, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-47591
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 19, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  mptcp: remove tcp ulp setsockopt support  TCP_ULP setsockopt cannot be used for mptcp because its already used internally to plumb subflow (tcp) sockets to the mptcp layer.  syzbot managed to trigger a crash for mptcp connections that are in fallback mode:  KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027] CPU: 1 PID: 1083 Comm: syz-executor.3 Not tainted 5.16.0-rc2-syzkaller #0 RIP: 0010:tls_build_proto net/tls/tls_main.c:776 [inline] [..]  __tcp_set_ulp net/ipv4/tcp_ulp.c:139 [inline]  tcp_set_ulp+0x428/0x4c0 net/ipv4/tcp_ulp.c:160  do_tcp_setsockopt+0x455/0x37c0 net/ipv4/tcp.c:3391  mptcp_setsockopt+0x1b47/0x2400 net/mptcp/sockopt.c:638  Remove support for TCP_ULP setsockopt.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.15.15-1 | [DEBIAN-CVE-2021-47591](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47591.md) | Jun 19, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.15.15-1 | [DEBIAN-CVE-2021-47591](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47591.md) | Jun 19, 2024 |
| Linux | linux Debian 14 | 5.15.15-1 | [DEBIAN-CVE-2021-47591](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47591.md) | Jun 19, 2024 |

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