In the Linux kernel, the following vulnerability has been resolved:
sctp: disable BH before calling udp_tunnel_xmit_skb()
udp_tunnel_xmit_skb() / udp_tunnel6_xmit_skb() are expected to run with
BH disabled. After commit 6f1a9140ecda ("add xmit recursion limit to
tunnel xmit functions"), on the path:
udp(6)_tunnel_xmit_skb() -> ip(6)tunnel_xmit()
dev_xmit_recursion_inc()/dec() must stay balanced on the same CPU.
Without local_bh_disable(), the context may move between CPUs, which can
break the inc/dec pairing. This may lead to incorrect recursion level
detection and cause packets to be dropped in ip(6)_tunnel_xmit() or
__dev_queue_xmit().
Fix it by disabling BH around both IPv4 and IPv6 SCTP UDP xmit paths.
In my testing, after enabling the SCTP over UDP:
# ip net exec ha sysctl -w net.sctp.udp_port=9899
# ip net exec ha sysctl -w net.sctp.encap_port=9899
# ip net exec hb sysctl -w net.sctp.udp_port=9899
# ip net exec hb sysctl -w net.sctp.encap_port=9899
# ip net exec ha iperf3 -s
# ip net exec hb iperf3 -c 192.168.0.1 --sctp
[ 5] 0.00-10.00 sec 37.2 MBytes 31.2 Mbits/sec sender
[ 5] 0.00-10.00 sec 37.1 MBytes 31.1 Mbits/sec receiver
# ip net exec hb iperf3 -c 192.168.0.1 --sctp
[ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec sender
[ 5] 0.00-10.00 sec 3.14 GBytes 2.69 Gbits/sec receiver
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). 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 low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (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)14 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (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