CVE-2026-98042 bpf: Don't resurrect a scalar id dropped by collect_linked_regs()
A logic error in the Linux kernel BPF verifier allows local attackers to potentially escalate privileges or execute code by exploiting register state inconsistencies.
- 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-2026-98042?
CVE-2026-98042 is a vulnerability in Linux, published on 25 Sep 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:
bpf: Don't resurrect a scalar id dropped by collect_linked_regs()
check_cond_jmp_op() copies the compared registers into env->{false,true}_reg{1,2} before collect_linked_regs() runs and copies those snapshots back into both branch states afterwards.
collect_linked_regs() records at most LINKED_REGS_MAX members of a linked registers group in the jump history and calls clear_scalar_id() for every member that does not fit. The compared register is not exempt from that.
As a consequence, sync_linked_regs() might adjust ranges for more registers than bpf_bt_sync_linked_regs() can propagate precision to.
Collect the linked registers before the snapshots are taken instead. This might lead to some unnecessary clear_scalar_id's, but from previous testing situations with many linked registers are extremely rare.
Which versions are affected by CVE-2026-98042?
How do I fix CVE-2026-98042?
Apply the vendor's patch.
Is CVE-2026-98042 being exploited?
There is no known exploitation of CVE-2026-98042 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-98042, GHSA-2742-pgwr-hw5x, UBUNTU-CVE-2026-98042.