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CVE-2021-47591

mptcp: remove tcp ulp setsockopt support

Medium5.5EPSS 0.21%
Published
Updated
Reserved
Assigned by
Linux

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.

Timeline

  1. ID reserved

    By Linux

  2. · 26 days later

    Published

  3. · 23 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2021-47591, by who scored it
Scored byCVSSScoreVector
NVDNVD · Modified3.1Medium5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.21% · top 89% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: no · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Weakness

Affected products

  • Linux · Linux

    • affected d9e4c129181004ec94b315b0c9db5eeb09da75e6 – < 3de0c86d42f841d1d64f316cd949e65c566f0734
    • affected d9e4c129181004ec94b315b0c9db5eeb09da75e6 – < 404cd9a22150f24acf23a8df2ad0c094ba379f57

  • Linux · Linux

    • affected 5.13
    • unaffected < 5.13
    • unaffected 5.15.11 – ≤ 5.15.*
    • unaffected 5.16 – ≤ *

References (2)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .