openvswitch: fix GSO userspace truncation underflow
Priority MEDIUM 50CWE-191Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 13 fixed, 5 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-191 and the CVSS impact.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00552 46th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.10.265, 5.15.216, 6.1.183 +5Red Hat: 3 advisoriesRed Hat: 13 fixed, 5 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.265, 5.15.216, 6.1.183, 6.6.148, 6.12.101, 6.18.42, 7.1.6, 7.2
Red Hat 3 advisories
- RHSA-2026:89197 Released 2026-10-27 · Red Hat rating CriticalOpenShift Container Platform 4.22.20 bug fix and security update
- Red Hat OpenShift Container Platform 4.22 rhcos-aarch64-4.22.9.8.202610241758-0, rhcos-ppc64le-4.22.9.8.202610241758-0, rhcos-s390x-4.22.9.8.202610241758-0 +1
- RHSA-2026:81552 Released 2026-10-13 · Red Hat rating Importantkernel security update
- Red Hat Enterprise Linux AppStream (v. 9) kernel-64k-debug-devel-5.14.0-687.57.1.el9_8, kernel-64k-debug-devel-matched-5.14.0-687.57.1.el9_8, kernel-64k-devel-5.14.0-687.57.1.el9_8 +12
- Red Hat Enterprise Linux BaseOS (v. 9) kernel-5.14.0-687.57.1.el9_8, kernel-64k-5.14.0-687.57.1.el9_8, kernel-64k-core-5.14.0-687.57.1.el9_8 +28
- Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) kernel-tools-libs-devel-5.14.0-687.57.1.el9_8, libperf-5.14.0-687.57.1.el9_8
- Red Hat Enterprise Linux Real Time (v. 9) kernel-rt-5.14.0-687.57.1.el9_8, kernel-rt-64k-5.14.0-687.57.1.el9_8, kernel-rt-64k-core-5.14.0-687.57.1.el9_8 +21
- Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt-5.14.0-687.57.1.el9_8, kernel-rt-core-5.14.0-687.57.1.el9_8, kernel-rt-debug-5.14.0-687.57.1.el9_8 +9
- RHSA-2026:81406 Released 2026-10-12 · Red Hat rating Importantkernel security, bug fix, and enhancement update
- 10Base-SMTV kernel-modules-internal-6.12.0-211.65.1.el10_2
- Red Hat Enterprise Linux AppStream (v. 10) kernel-64k-debug-devel-6.12.0-211.65.1.el10_2, kernel-64k-debug-devel-matched-6.12.0-211.65.1.el10_2, kernel-64k-devel-6.12.0-211.65.1.el10_2 +12
- Red Hat Enterprise Linux BaseOS (v. 10) kernel-6.12.0-211.65.1.el10_2, kernel-64k-6.12.0-211.65.1.el10_2, kernel-64k-core-6.12.0-211.65.1.el10_2 +29
- Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) kernel-tools-libs-devel-6.12.0-211.65.1.el10_2, libperf-6.12.0-211.65.1.el10_2
- Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal-6.12.0-211.65.1.el10_2
- Red Hat Enterprise Linux Real Time (v. 10) kernel-rt-6.12.0-211.65.1.el10_2, kernel-rt-64k-6.12.0-211.65.1.el10_2, kernel-rt-64k-core-6.12.0-211.65.1.el10_2 +21
- Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt-6.12.0-211.65.1.el10_2, kernel-rt-core-6.12.0-211.65.1.el10_2, kernel-rt-debug-6.12.0-211.65.1.el10_2 +9
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | — |
| Red Hat Enterprise Linux 7 | Affected | No fix yet |
| Red Hat Enterprise Linux 8 | Affected | No fix yet |
| Red Hat Enterprise Linux 9 | Affected | No fix yet |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet |
| 10Base-SMTV | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux AppStream (v. 10) | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux AppStream (v. 9) | Fixed | RHSA-2026:81552 |
| Red Hat Enterprise Linux BaseOS (v. 10) | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux BaseOS (v. 9) | Fixed | RHSA-2026:81552 |
| Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) | Fixed | RHSA-2026:81552 |
| Red Hat Enterprise Linux Hidden (v. 10) | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux Real Time (v. 10) | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux Real Time (v. 9) | Fixed | RHSA-2026:81552 |
| Red Hat Enterprise Linux Real Time for NFV (v. 10) | Fixed | RHSA-2026:81406 |
| Red Hat Enterprise Linux Real Time for NFV (v. 9) | Fixed | RHSA-2026:81552 |
| Red Hat OpenShift Container Platform 4.22 | Fixed | RHSA-2026:89197 |
Not affected: 2 products
- Red Hat Enterprise Linux for NVIDIA 26
- Red Hat OpenShift Container Platform 4
Timeline
- 2026-10-02 Threatist record created from CVE-2026-68123
- 2026-10-03 Alias added: GHSA-wf82-h5xg-m662
- 2026-10-13 Fix available: RHSA-2026:81406 · Red Hat
- 2026-10-13 Fix available: RHSA-2026:81552 · Red Hat
- 2026-10-13 Fix available: 10Base-SMTV, Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9) +9 · Red Hat
- 2026-10-16 CISA SSVC decision points changed
- 2026-10-20 Weakness changed · CISA ADP
- 2026-10-28 Fix available: Red Hat OpenShift Container Platform 4.22 · Red Hat
- 2026-10-29 Fix available: RHSA-2026:89197 · Red Hat
- 2026-10-30 Affected versions changed · Red Hat
References
Other 8
- https://git.kernel.org/stable/c/50a6a85f3d6b1d22d8436848606cdef5d2c490b4
- https://git.kernel.org/stable/c/2623c48cc3a8da9a1886fd8f65c0e348f4406fd6
- https://git.kernel.org/stable/c/e211b081901ffca76674082c73eeaed53524c369
- https://git.kernel.org/stable/c/a16eaaf7c0b0ccdef6166707d90ffbc6eebf6855
- https://git.kernel.org/stable/c/fbfa3ad2ad6f3a5624aba5211c46290fb98cc9dc
- https://git.kernel.org/stable/c/100a23b1613e9218e0af654ef102352c713f0263
- https://git.kernel.org/stable/c/ea85dbcbe8d4056ecb54352f97743d138ea4c407
- https://git.kernel.org/stable/c/4032f8ed10fcb84d41c508dfb04be96589f78dfe
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Sources
- CVE-2026-68123 · CVE Program
- CVE-2026-68123 · NVD
- FIRST EPSS
- GHSA-wf82-h5xg-m662 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-68123 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences