Critical

CVE-2026-68123 — openvswitch: fix GSO userspace truncation underflow

In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix GSO userspace truncation underflow OVS_ACTION_ATTR_TRUNC currently stores a delta from the original skb length in OVS_CB(skb)->cutlen. When a later userspace action segments a GSO skb, queue_gso_packets() reuses that delta for each smaller segment. A segment can then reach queue_userspace_packet() with cutlen greater than skb->len, underflowing the length passed to skb_zerocopy(). Store the maximum preserved length instead and bound each consumer against the current skb length. Use U32_MAX as the no-truncation sentinel so the value remains valid if skb geometry changes before a consumer handles it.

Published Aug 10, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.6% (30-day exploitation probability)+7
Technical severity (critical)+10

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.55%

ahead of 45% of scored CVEs · Oct 15, 2026

Affects

Linux

CVSS base

9.8

Critical · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < 50a6a85f3d6b1d22d8436848606cdef5d2c490b4≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < 2623c48cc3a8da9a1886fd8f65c0e348f4406fd6≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < e211b081901ffca76674082c73eeaed53524c369≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < 100a23b1613e9218e0af654ef102352c713f0263≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < ea85dbcbe8d4056ecb54352f97743d138ea4c407≥ f2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 and < 4032f8ed10fcb84d41c508dfb04be96589f78dfe and 1 more version 4.8	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.8	CVSS 3.1	Critical	3.9	5.9	416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database
9.8	CVSS 3.1	Critical	—	—	Linux via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67)

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 9.8
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Received
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Aug 10, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc
NIST National Vulnerability Database
git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4
NIST National Vulnerability Database
git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263
NIST National Vulnerability Database
git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe
NIST National Vulnerability Database
git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6
NIST National Vulnerability Database
git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369
NIST National Vulnerability Database
git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407
NIST National Vulnerability Database
git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 15h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 15h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-68123 is "openvswitch: fix GSO userspace truncation underflow", rated Critical. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.8 describes technical severity. EPSS 0.55% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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