CVE-2026-74726
In the Linux kernel, the following vulnerability has been resolved:
bonding: alb: re-check primary_is_promisc under RTNL in bond_alb_monitor
bond_alb_monitor() reads primary_is_promisc under RCU, then drops RCU and
takes RTNL via rtnl_trylock() before undoing the promiscuity it set on the
active slave. In that window the active slave can change under RTNL
(RTM_DELLINK -> __bond_release_one() -> bond_alb_handle_active_change()),
which already drops the promiscuity and clears primary_is_promisc. The
monitor still acts on the stale decision: if the slave was removed with no
failover, curr_active_slave is now NULL and the deref faults; if it failed
over, the stale dev_set_promiscuity(-1) underflows the new slave's
promiscuity counter and pins it in IFF_PROMISC.
Oops: general protection fault, probably for non-canonical address ...
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
Workqueue: b42 bond_alb_monitor
RIP: 0010:bond_alb_monitor (drivers/net/bonding/bond_alb.c:1600)
process_one_work (kernel/workqueue.c:3322)
worker_thread (kernel/workqueue.c:3486)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
Kernel panic - not syncing: Fatal exception
Re-check primary_is_promisc (and curr_active_slave) after taking RTNL so
the monitor only undoes an increment it still owns. The other bonding
monitors already re-read state under RTNL in their commit phase
(bond_miimon_commit/bond_ab_arp_commit); bond_alb_monitor() was the only
one acting on the pre-trylock decision.
CSIRTS triage
- What
- The bonding driver alb mode has a race condition in primary_is_promisc check in bond_alb_monitor.
- Who is affected
- Systems running affected Linux kernel versions with bonding in ALB mode.
- Urgency
- Medium severity (CVSS 4.7); not currently exploited but can cause inconsistent state.
- Action
- Update to a patched Linux kernel version addressing CVE-2026-74726.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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