In the Linux kernel, the following vulnerability has been resolved:
vmxnet3: Fix malformed packet sizing in vmxnet3_process_xdp
vmxnet3 driver's XDP handling is buggy for packet sizes using ring0 (that
is, packet sizes between 128 - 3k bytes).
We noticed MTU-related connectivity issues with Cilium's service load-
balancing in case of vmxnet3 as NIC underneath. A simple curl to a HTTP
backend service where the XDP LB was doing IPIP encap led to overly large
packet sizes but only for *some* of the packets (e.g. HTTP GET request)
while others (e.g. the prior TCP 3WHS) looked completely fine on the wire.
In fact, the pcap recording on the backend node actually revealed that the
node with the XDP LB was leaking uninitialized kernel data onto the wire
for the affected packets, for example, while the packets should have been
152 bytes their actual size was 1482 bytes, so the remainder after 152 bytes
was padded with whatever other data was in that page at the time (e.g. we
saw user/payload data from prior processed packets).
We only noticed this through an MTU issue, e.g. when the XDP LB node and
the backend node both had the same MTU (e.g. 1500) then the curl request
got dropped on the backend node's NIC given the packet was too large even
though the IPIP-encapped packet normally would never even come close to
the MTU limit. Lowering the MTU on the XDP LB (e.g. 1480) allowed to let
the curl request succeed (which also indicates that the kernel ignored the
padding, and thus the issue wasn't very user-visible).
Commit e127ce7699c1 ("vmxnet3: Fix missing reserved tailroom") was too eager
to also switch xdp_prepare_buff() from rcd->len to rbi->len. It really needs
to stick to rcd->len which is the actual packet length from the descriptor.
The latter we also feed into vmxnet3_process_xdp_small(), by the way, and
it indicates the correct length needed to initialize the xdp->{data,data_end}
parts. For e127ce7699c1 ("vmxnet3: Fix missing reserved tailroom") the
relevant part was adapting xdp_init_buff() to address the warning given the
xdp_data_hard_end() depends on xdp->frame_sz. With that fixed, traffic on
the wire looks good again.
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
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-23). 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; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade 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; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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