In the Linux kernel, the following vulnerability has been resolved:
ipv4: Fix reference count leak when using error routes with nexthop objects
When a nexthop object is deleted, it is marked as dead and then
fib_table_flush() is called to flush all the routes that are using the
dead nexthop.
The current logic in fib_table_flush() is to only flush error routes
(e.g., blackhole) when it is called as part of network namespace
dismantle (i.e., with flush_all=true). Therefore, error routes are not
flushed when their nexthop object is deleted:
# ip link add name dummy1 up type dummy
# ip nexthop add id 1 dev dummy1
# ip route add 198.51.100.1/32 nhid 1
# ip route add blackhole 198.51.100.2/32 nhid 1
# ip nexthop del id 1
# ip route show
blackhole 198.51.100.2 nhid 1 dev dummy1
As such, they keep holding a reference on the nexthop object which in
turn holds a reference on the nexthop device, resulting in a reference
count leak:
# ip link del dev dummy1
[ 70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2
Fix by flushing error routes when their nexthop is marked as dead.
IPv6 does not suffer from this problem.
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
- 0.1% 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 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