MEDIUM Public exploit Introduced in 5.6
netfilter IPSet Leak
CVE-2026-31418
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
KernelScan AI5.5MEDIUM
01Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: ipset: drop logically empty buckets in mtype_del mtype_del() counts empty slots below n->pos in k, but it only drops the bucket when both n->pos and k are zero. This misses buckets whose live entries have all been removed while n->pos still points past deleted slots. Treat a bucket as empty when all positions below n->pos are unused and release it directly instead of shrinking it further.
02KernelScan AI Analysis
Risk summary
A memory leak in netfilter ipset hash bucket management allows local attackers with CAP_NET_ADMIN (obtainable via user namespaces on default kernels) to exhaust system memory by repeatedly creating and deleting ipset entries. This leads to system-wide denial of service through memory exhaustion.
Vulnerability analysis
The mtype_del() function incorrectly determines when hash buckets are empty and should be freed. The original logic only freed buckets when both n->pos and k were zero, missing cases where all live entries below n->pos had been deleted while n->pos still pointed past deleted slots. The fix changes the condition to k == n->pos, properly identifying logically empty buckets for immediate release instead of leaving them allocated.
Exploit availability
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Lifecycle
03Fix Versions
| Branch | Introduced | Fixed in | Patch commit |
|---|---|---|---|
| 5.10 | 5.6 | 5.10.253 | ad92ee87462f |
| 5.15 | 5.6 | 5.15.203 | 6cea34d7ec68 |
| 5.4 | 5.4.24 | 5.5 | c098ff857e7c |
| 5.5 | 5.5.8 | 5.6 | 58f3a14826d4 |
| 6.1 | 5.6 | 6.1.168 | b7eef00f08b9 |
| 6.12 | 5.6 | 6.12.81 | ceacaa76f221 |
| 6.18 | 5.6 | 6.18.22 | 9862ef9ab0a1 |
| 6.19 | 5.6 | 6.19.12 | — |
| 6.6 | 5.6 | 6.6.134 | 68ca0eea0af0 |
| mainline | 5.6 | 7.0 | — |
| cip/5.10 | 5.6 | 5.10.254-cip72 | c098ff857e7c |
| cip/5.10-rt | 5.6 | 5.10.254-cip72-rt32 | c098ff857e7c |
| cip/6.1 | 5.6 | 6.1.169-cip54 | ad92ee87462f |
| cip/6.1-rt | 5.6 | 6.1.175-cip57-rt30 | ad92ee87462f |
| cip/6.12 | 5.6 | 6.12.83-cip21 | b7eef00f08b9 |
04CIP Kernels
State of the newest release of each Civil Infrastructure Platform SLTS tree, from CIP's own fix records.
| CIP tree | State |
|---|---|
| cip/6.12 | Fixed in 6.12.83-cip21 |
| cip/6.1 | Fixed in 6.1.169-cip54 |
| cip/6.1-rt | Fixed in 6.1.175-cip57-rt30 |
| cip/5.10 | Fixed in 5.10.254-cip72 |
| cip/5.10-rt | Fixed in 5.10.254-cip72-rt32 |