5.5

CVE-2021-47593: mptcp: clear 'kern' flag from fallback sockets

Modified
AliasesUBUNTU-CVE-2021-47593DEBIAN-CVE-2021-47593
Published 19-06-2024Last modified 11-05-2026

Vulnerability summary

CVE-2021-47593 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 16% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.25%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 3
SUSE-SU-2024:2894-1SUSE-SU-2024:2939-1SUSE-SU-2024:2947-1

Timeline

  1. 19-06-2024
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: clear 'kern' flag from fallback sockets The mptcp ULP extension relies on sk->sk_sock_kern being set correctly: It prevents setsockopt(fd, IPPROTO_TCP, TCP_ULP, "mptcp", 6); from working for plain tcp sockets (any userspace-exposed socket). But in case of fallback, accept() can return a plain tcp sk. In such case, sk is still tagged as 'kernel' and setsockopt will work. This will crash the kernel, The subflow extension has a NULL ctx->conn mptcp socket: BUG: KASAN: null-ptr-deref in subflow_data_ready+0x181/0x2b0 Call Trace: tcp_data_ready+0xf8/0x370 [..]

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.25%

Chance of exploitation in the next 30 days

Percentile

16%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.25% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu62 products
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
  • linux-aws-5.13All versions (No fix recorded)
  • linux-aws-5.19All versions (No fix recorded)
Linux2 products
  • linux≥ cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be, < 451f1eded7f56e93aaf52eb547ba97742d9c0e97 | ≥ cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be, < c26ac0ea3a91c210cf90452e625dc441adf3e549 | ≥ cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be, < d6692b3b97bdc165d150f4c1505751a323a80717 | 5.6
  • linux_kernel≥ 5.6, < 5.10.88 | ≥ 5.11, < 5.15.11 | 5.16:rc1 | 5.16:rc2 | 5.16:rc3 | 5.16:rc4 | 5.16:rc5
Debian1 product
  • linux< 5.15.15-1

3 vendors · 65 products

References

7 links