In the Linux kernel, the following vulnerability has been resolved:
ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()
When querying a nexthop object via RTM_GETNEXTHOP, the kernel currently
allocates a fixed-size skb using NLMSG_GOODSIZE. While sufficient for
single nexthops and small Equal-Cost Multi-Path groups, this fixed
allocation fails for large nexthop groups like 512 nexthops.
This results in the following warning splat:
WARNING: net/ipv4/nexthop.c:3395 at rtm_get_nexthop+0x176/0x1c0, CPU#20: rep/4608
[...]
RIP: 0010:rtm_get_nexthop (net/ipv4/nexthop.c:3395)
[...]
Call Trace:
<TASK>
rtnetlink_rcv_msg (net/core/rtnetlink.c:6989)
netlink_rcv_skb (net/netlink/af_netlink.c:2550)
netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)
netlink_sendmsg (net/netlink/af_netlink.c:1894)
____sys_sendmsg (net/socket.c:721 net/socket.c:736 net/socket.c:2585)
___sys_sendmsg (net/socket.c:2641)
__sys_sendmsg (net/socket.c:2671)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
</TASK>
Fix this by allocating the size dynamically using nh_nlmsg_size() and
using nlmsg_new(), this is consistent with nexthop_notify() behavior. In
addition, adjust nh_nlmsg_size_grp() so it calculates the size needed
based on flags passed. While at it, also add the size of NHA_FDB for
nexthop group size calculation as it was missing too.
This cannot be reproduced via iproute2 as the group size is currently
limited and the command fails as follows:
addattr_l ERROR: message exceeded bound of 1048
References
Configurations
Configuration 1 (hide)
|
History
28 Apr 2026, 17:38
| Type | Values Removed | Values Added |
|---|---|---|
| CPE | cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:* |
|
| CWE | NVD-CWE-noinfo | |
| References | () https://git.kernel.org/stable/c/14cf0cd35361f4e94824bf8a42f72713d7702a73 - Patch | |
| References | () https://git.kernel.org/stable/c/40bd39e383a0478fd5c221f393df05fd9d70cfbc - Patch | |
| References | () https://git.kernel.org/stable/c/615517f3f8d53b0cf41507c7599971e17adfdfa5 - Patch | |
| References | () https://git.kernel.org/stable/c/635038fe19db391117e66b46bdc2b6e447ac801d - Patch | |
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 5.5 |
| First Time |
Linux
Linux linux Kernel |
23 Apr 2026, 12:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-04-23 12:17
Updated : 2026-04-28 17:38
NVD link : CVE-2026-31531
Mitre link : CVE-2026-31531
CVE.ORG link : CVE-2026-31531
JSON object : View
Products Affected
linux
- linux_kernel
CWE