Integer truncation in Linux kernel BPF flow dissector
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Partial Red Hat: 6 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
The Linux kernel from 4.20 is affected in its BPF flow dissector. When hlen exceeds 65535, the upper clamp bound is truncated to a u16 in bpf_flow_dissect(), so the offsets nhoff and thoff are forced to zero even when the BPF program returned valid values.
Written with Claude Haiku 5.5 from the sources below · 2026-11-07
Description from the CNA
In the Linux kernel, the following vulnerability has been resolved: flow_dissector: avoid u16 truncation of hlen in bpf_flow_dissect() bpf_flow_dissect() sanitizes the offsets returned by the BPF program with clamp_t(u16, ..., hlen). If hlen is bigger than 65535, the upper bound is truncated before the comparison. For instance, with hlen == 65536, both nhoff and thoff are forced to zero, even if the program returned sane values. This is the same class of bug as the one fixed in commit 99bda1ecbd56 ("flow_dissector: avoid u16 truncation of skb->len when computing thoff"). That fix does not cover the BPF path, because __skb_flow_dissect() returns early when a BPF flow dissector handles the packet. struct bpf_flow_keys stores nhoff and thoff as u16, so cap hlen to U16_MAX before clamping. Found by sashiko while reviewing the commit above.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 4.20 and later | 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3 | Patch available | CNA |
- Linux VendorLinux Affected 4.20 and later Fixed in 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3 Patch available CNA
Remediation
Update the Linux kernel to 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11 or 7.3, depending on the stable branch in use. Red Hat Enterprise Linux 10, 8 and 9 and Red Hat OpenShift Container Platform 4 and 5 are affected with no fix available, and Red Hat Enterprise Linux 6 is affected with no fix planned.
Written with Claude Haiku 5.5 from the sources below · 2026-11-07
- Fix · CNA Linux (Linux) Fixed in 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Not affected: 1 product
- Red Hat Enterprise Linux 7
Timeline
- 2026-10-23 Threatist record created from CVE-2026-98950
- 2026-10-23 Alias added: GHSA-4jwg-g8h6-9gv7
- 2026-10-29 Affected versions changed · Red Hat
- 2026-10-29 CVSS score added · Red Hat
- 2026-10-30 Fix available: Linux/Linux@46d21495f633e38d40857401504ee51c56ffed2a, Linux/[email protected], Linux/[email protected] +3 · CNA
- 2026-10-30 3 new references · CNA
- 2026-11-07 Affected versions changed · Red Hat
References
Other 8
- https://git.kernel.org/stable/c/46d21495f633e38d40857401504ee51c56ffed2a
- https://git.kernel.org/stable/c/6267f8304cbd9ec9f3f53bd227a733e07131492e
- https://git.kernel.org/stable/c/99c59062172620a0bac4ae8cf37c83bb78772cdd
- https://git.kernel.org/stable/c/c44c02c930c6583b235a1937c69ff716c4bb4514
- https://git.kernel.org/stable/c/3fb5ad2951a6df92c98f4f06cd70f20c50a2eb2a
- https://git.kernel.org/stable/c/cc18eb0e9941162c03f03f411ed7f6c339d91fa0
- https://git.kernel.org/stable/c/61b43a51a55929ec040bee3ea51af2121b956d05
- https://git.kernel.org/stable/c/f202578efc738b883cfa04889eb97328914265a7
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Sources
- CVE-2026-98950 · CVE Program
- CVE-2026-98950 · NVD
- FIRST EPSS
- GHSA-4jwg-g8h6-9gv7 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-98950 · Red Hat security data · CC BY 4.0
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