Linux kernel ipv4 exception dump NULL dereference when nexthop group shrinks
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: 4 without a fix
No CVSS vector from any source. Fix status from CNA and Red Hat.
Summary
The IPv4 FIB dump code in the Linux kernel can dereference a NULL pointer. Commit 4ce5dc9316de let inet_dump_fib() run concurrently with nexthop replacement. If RTM_NEWNEXTHOP replaces a group with fewer paths after fib_dump_info_fnhe() reads the path count but before it reloads nh->nh_grp, fib_info_nhc() returns NULL and the dump dereferences it through nhc_flags.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
Description from the CNA
In the Linux kernel, the following vulnerability has been resolved: ipv4: stop exception dump when nexthop group shrinks Commit 4ce5dc9316de ("inet: switch inet_dump_fib() to RCU protection") allowed IPv4 FIB dumps to run concurrently with nexthop replacement. fib_dump_info_fnhe() uses fib_info_num_path() as the loop bound, then fib_info_nhc() independently reloads nh->nh_grp. If RTM_NEWNEXTHOP replaces a group with fewer paths between those loads, fib_info_nhc() returns NULL and the dump dereferences it through nhc_flags. Stop the walk when the indexed path is absent. Nexthop groups are dense, so the current snapshot has no later path.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
Install a kernel that contains the fix: 6.12.113, 6.18.57, 7.2.11 or 7.3. Affected versions start at 6.9. Red Hat Enterprise Linux 9 and 10 and Red Hat OpenShift Container Platform 4 have no fix available, and Red Hat Enterprise Linux 6 has no fix planned.
Written with Claude Haiku 5.5 from the sources below · 2026-11-06
- Fix · CNA Linux (Linux) Fixed in 6.12.113, 6.18.57, 7.2.11, 7.3
Vendor assessments
Red Hat
Red Hat rating: Moderate. 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 9 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
Not affected: 4 products
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
- Red Hat OpenShift Container Platform 4
Timeline
- 2026-10-23 Threatist record created from CVE-2026-99073
- 2026-10-23 Alias added: GHSA-4527-q5wc-xrv7
- 2026-10-26 Affected versions changed · Red Hat
- 2026-10-26 CVSS score added · Red Hat
References
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Sources
- CVE-2026-99073 · CVE Program
- CVE-2026-99073 · NVD
- FIRST EPSS
- GHSA-4527-q5wc-xrv7 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-99073 · Red Hat security data · CC BY 4.0
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