CVE-2026-43085 netfilter: nfnetlink_log: initialize nfgenmsg in NLMSG_DONE terminator
A Linux kernel netfilter bug leaks stale kernel heap data to userspace via uninitialized netlink message terminators, allowing local attackers to read sensitive memory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43085?
CVE-2026-43085 is a medium-severity vulnerability in Linux kernel, published on 6 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nfnetlink_log: initialize nfgenmsg in NLMSG_DONE terminator
When batching multiple NFLOG messages (inst->qlen > 1), __nfulnl_send() appends an NLMSG_DONE terminator with sizeof(struct nfgenmsg) payload via nlmsg_put(), but never initializes the nfgenmsg bytes. The nlmsg_put() helper only zeroes alignment padding after the payload, not the payload itself, so four bytes of stale kernel heap data are leaked to userspace in the NLMSG_DONE message body.
Use nfnl_msg_put() to build the NLMSG_DONE terminator, which initializes the nfgenmsg payload via nfnl_fill_hdr(), consistent with how __build_packet_message() already constructs NFULNL_MSG_PACKET headers.
Which versions are affected by CVE-2026-43085?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43085?
Apply the vendor's patch.
Is CVE-2026-43085 being exploited?
There is no known exploitation of CVE-2026-43085 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43085, DEBIAN-CVE-2026-43085, GHSA-rp69-c9w2-rv4p, ROOT-OS-DEBIAN-11-CVE-2026-43085, ROOT-OS-DEBIAN-12-CVE-2026-43085, ROOT-OS-UBUNTU-2204-CVE-2026-43085 and 2 more.