In the Linux kernel, the following vulnerability has been resolved:
mptcp: prevent BPF accessing lowat from a subflow socket.
Alexei reported the following splat:
WARNING: CPU: 32 PID: 3276 at net/mptcp/subflow.c:1430 subflow_data_ready+0x147/0x1c0
Modules linked in: dummy bpf_testmod(O) [last unloaded: bpf_test_no_cfi(O)]
CPU: 32 PID: 3276 Comm: test_progs Tainted: GO 6.8.0-12873-g2c43c33bfd23
Call Trace:
mptcp_set_rcvlowat+0x79/0x1d0
sk_setsockopt+0x6c0/0x1540
__bpf_setsockopt+0x6f/0x90
bpf_sock_ops_setsockopt+0x3c/0x90
bpf_prog_509ce5db2c7f9981_bpf_test_sockopt_int+0xb4/0x11b
bpf_prog_dce07e362d941d2b_bpf_test_socket_sockopt+0x12b/0x132
bpf_prog_348c9b5faaf10092_skops_sockopt+0x954/0xe86
__cgroup_bpf_run_filter_sock_ops+0xbc/0x250
tcp_connect+0x879/0x1160
tcp_v6_connect+0x50c/0x870
mptcp_connect+0x129/0x280
__inet_stream_connect+0xce/0x370
inet_stream_connect+0x36/0x50
bpf_trampoline_6442491565+0x49/0xef
inet_stream_connect+0x5/0x50
__sys_connect+0x63/0x90
__x64_sys_connect+0x14/0x20
The root cause of the issue is that bpf allows accessing mptcp-level
proto_ops from a tcp subflow scope.
Fix the issue detecting the problematic call and preventing any action.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-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 2026-10-27). 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