CVE-2021-47594

MEDIUMNVD 5.55.5

Also known asEUVD-2021-34596 (ENISA EUVD) · GHSA-34pw-x3jp-c8x5 (GitHub Security Advisories)Source: ENISA EUVD

5.5EG

EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).

Lower severity and no public exploit yet

CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.5Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

In the Linux kernel, the following vulnerability has been resolved:

mptcp: never allow the PM to close a listener subflow

Currently, when deleting an endpoint the netlink PM treverses all the local MPTCP sockets, regardless of their status.

If an MPTCP listener socket is bound to the IP matching the delete endpoint, the listener TCP socket will be closed. That is unexpected, the PM should only affect data subflows.

Additionally, syzbot was able to trigger a NULL ptr dereference due to the above:

general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] CPU: 1 PID: 6550 Comm: syz-executor122 Not tainted 5.16.0-rc4-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__lock_acquire+0xd7d/0x54a0 kernel/locking/lockdep.c:4897 Code: 0f 0e 41 be 01 00 00 00 0f 86 c8 00 00 00 89 05 69 cc 0f 0e e9 bd 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 0f 85 f3 2f 00 00 48 81 3b 20 75 17 8f 0f 84 52 f3 ff RSP: 0018:ffffc90001f2f818 EFLAGS: 00010016 RAX: dffffc0000000000 RBX: 0000000000000018 RCX: 0000000000000000 RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000001 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000000 R11: 000000000000000a R12: 0000000000000000 R13: ffff88801b98d700 R14: 0000000000000000 R15: 0000000000000001 FS: 00007f177cd3d700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f177cd1b268 CR3: 000000001dd55000 CR4: 0000000000350ee0 Call Trace: lock_acquire kernel/locking/lockdep.c:5637 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162 finish_wait+0xc0/0x270 kernel/sched/wait.c:400 inet_csk_wait_for_connect net/ipv4/inet_connection_sock.c:464 [inline] inet_csk_accept+0x7de/0x9d0 net/ipv4/inet_connection_sock.c:497 mptcp_accept+0xe5/0x500 net/mptcp/protocol.c:2865 inet_accept+0xe4/0x7b0 net/ipv4/af_inet.c:739 mptcp_stream_accept+0x2e7/0x10e0 net/mptcp/protocol.c:3345 do_accept+0x382/0x510 net/socket.c:1773 __sys_accept4_file+0x7e/0xe0 net/socket.c:1816 __sys_accept4+0xb0/0x100 net/socket.c:1846 __do_sys_accept net/socket.c:1864 [inline] __se_sys_accept net/socket.c:1861 [inline] __x64_sys_accept+0x71/0xb0 net/socket.c:1861 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f177cd8b8e9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f177cd3d308 EFLAGS: 00000246 ORIG_RAX: 000000000000002b RAX: ffffffffffffffda RBX: 00007f177ce13408 RCX: 00007f177cd8b8e9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007f177ce13400 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f177ce1340c R13: 00007f177cde1004 R14: 6d705f706374706d R15: 0000000000022000

Fix the issue explicitly skipping MPTCP socket in TCP_LISTEN status.

CVSS v3: 5.5
EG Score: 5.5MEDIUMmedium confidence
EG Risk: 25
EPSS PROB: 0.2%
EPSS %ILE: 11th
KEV: Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.

EG Severity: 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood: 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation: None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority: SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

June 19, 2024

Last Modified

November 21, 2024

References (2)

CVE Programhttps://git.kernel.org/stable/c/1456a0004cc54c58adb2501cb0c95dc8b3c83e9ePatch
CVE Programhttps://git.kernel.org/stable/c/b0cdc5dbcf2ba0d99785da5aabf1b17943805b8aPatch

Affected Packages

(3 across 3 ecosystems)

Debian:12(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.15.15-1: fixed in 5.15.15-1	—

Debian:13(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.15.15-1: fixed in 5.15.15-1	—

Debian:14(1)

Package	Vulnerable range	Fix by version range	Dependents
linux	—	every version up to 5.15.15-1: fixed in 5.15.15-1	—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-476NULL Pointer Dereference

Data Freshness Timeline

(refreshed 7× in last 7d / 36× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 97 of 204 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 3 repeat rows among the latest 100 are merged into the row they repeat. The 107 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

2026-11-02 16:38 UTCEPSS rescoreEPSS 0.2% · 11th percentile
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2026-10-24 21:41 UTCEG score recompute
2026-10-24 21:41 UTCGHSA enrichmentGHSA-34pw-x3jp-c8x5 · GitHub CVSS 5.5
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2026-10-12 16:30 UTCEPSS rescoreEPSS 0.2% · 10th percentile
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Same CWE

10 shown

CWE-476

Frequently asked(5)

What is CVE-2021-47594?

CVE-2021-47594 is a medium-severity vulnerability; its CVE record was published on June 19, 2024. In the Linux kernel, the following vulnerability has been resolved: mptcp: never allow the PM to close a listener subflow Currently, when deleting an endpoint the netlink PM treverses all the local MPTCP sockets, regardless of their status. If an MPTCP listener socket is bound to the IP matching…

When was the CVE record for CVE-2021-47594 published?

The CVE record for CVE-2021-47594 was published on June 19, 2024. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of November 21, 2024; the record at its source may have been updated since.

Is CVE-2021-47594 actively exploited?

CVE-2021-47594 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (11th percentile of EPSS-scored CVEs).

What is the CVSS score of CVE-2021-47594?

CVE-2021-47594 has a CVSS v3 base score of 5.5 (NVD).

How do I remediate CVE-2021-47594?

A fix for CVE-2021-47594 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

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CVE-2021-47594

📅 Published

🔄 Last Modified

🔗 References (2)