CVE-2026-74656
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
A use-after-free vulnerability was found in the Linux kernel's fib_nhc_update_mtu() function for IPv4. The issue stems from lack of synchronization between walking the PMTU exception table and updates, potentially leading to access to freed memory. An attacker could exploit this flaw to compromise system integrity.
Risk Assessment
The vulnerability could be exploited locally to escalate privileges or cause a kernel panic, posing a serious risk to organizational stability and security.
Recommendation
Immediately apply the official patch from the Linux kernel vendor and update systems to a patched version. Monitor security advisories and test patches in staging before production deployment.
Other vulnerabilities in Linux kernel
See all- CVE-2026-99215Unknown
In the Linux kernel power supply subsystem, a use-after-free vulnerability exists. If a power supply is unregistered while its external_power_changed() callback is still running, the driver may free data that the callback is still accessing, leading to a kernel crash (NULL pointer dereference).
- CVE-2026-99210Unknown
In the Linux kernel accel/rocket driver, rocket_probe() stores the return value of rocket_device_init() in the file-scoped rdev pointer before checking whether it is an error pointer. On failure rdev remains an ERR_PTR, and a later probe can skip initialization and dereference the error pointer when reading rdev->num_cores.
- CVE-2026-99209Unknown
In the Linux kernel drm/xe driver, xe_evict_flags() reads tbo->resource->mem_type, but a BO can reach eviction with no ttm.resource, e.g. an imported dma-buf whose resource was freed during teardown. This causes a NULL pointer dereference and a kernel fault.
- CVE-2026-99208Unknown
In the Linux kernel drm/xe/oa driver, ttm_bo_type_kernel BOs are not guaranteed to be zeroed on allocation and may contain data from previously freed pages. Since the OA buffer is mmap'able by userspace, this can expose stale kernel memory contents.
- CVE-2026-99207Unknown
In the Linux kernel's scsi: target subsystem, target_do_delayed_work() acquired delayed_cmd_lock with a plain spin_lock() without disabling interrupts, while all other acquisition sites use spin_lock_irqsave(). Since commands can now complete in interrupt context (complete_type=1 with direct_compl_supp), this can cause a deadlock when a completion arrives on the same CPU where the work item holds the lock.
- CVE-2026-99205Unknown
In the Linux kernel, a race exists in sched_change_end() with __sched_setscheduler() for queued but non-running tasks. When a task's scheduling class changes (e.g., from SCHED_OTHER to SCHED_RR), rq->next_class is not updated and the need-resched indicator is not set, causing the CPU to idle despite a runnable task being present.
- CVE-2026-99200Unknown
In the Linux kernel, the hisi_femac network driver (net: hisilicon) assigns netdev_ops only after connecting the PHY. With CONFIG_NET_SHAPER enabled, phy_attach_direct() reads uninitialized netdev_ops, causing a kernel panic from a NULL pointer dereference.
- CVE-2026-99199Unknown
In the Linux kernel, the hip04_eth network driver (net: hisilicon) calls of_phy_connect() before ndev->netdev_ops is assigned. With CONFIG_NET_SHAPER enabled, phy_attach_direct() reads uninitialized netdev_ops, causing a kernel panic from a NULL pointer dereference.
- CVE-2026-99198Unknown
In the Linux kernel, the owl_emac network driver (net: ethernet: actions) calls owl_emac_phy_init(), which connects the PHY, before netdev->netdev_ops is assigned. With CONFIG_NET_SHAPER enabled, phy_attach_direct() reads uninitialized netdev_ops, causing a kernel panic from a NULL pointer dereference.
- CVE-2026-99197Unknown
In the Linux kernel, the mv643xx_eth network driver connects the PHY before dev->netdev_ops is assigned. With CONFIG_NET_SHAPER enabled, phy_attach_direct() reads uninitialized netdev_ops, causing a kernel panic from a NULL pointer dereference.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ipv4: fix use-after-free in fib_nhc_update_mtu() fib_nhc_update_mtu() walks the nexthop exception table under RTNL, but RTNL does not serialize this walk with PMTU exception updates. The walk uses rcu_dereference_protected() with a constant true condition without holding fnhe_lock. The following interleaving can therefore occur: CPU 0 CPU 1 fib_nhc_update_mtu() update_or_create_fnhe() load fnhe spin_lock_bh(&fnhe_lock) fnhe_remove_oldest() unlink fnhe kfree_rcu(fnhe, rcu) <quiescent state> access fnhe after grace period KASAN reported: BUG: KASAN: slab-use-after-free in fib_nhc_update_mtu+0x3df/0x410 Read of size 8 at addr ffff888107d49000 by task poc/90 Call Trace: fib_nhc_update_mtu+0x3df/0x410 fib_sync_mtu+0x7a/0xd0 fib_netdev_event+0x229/0x3f0 netif_set_mtu_ext+0x33a/0x570 dev_set_mtu+0x88/0x120 The same walk updates fnhe_pmtu and fnhe_mtu_locked. These fields form a pair and other writers serialize them with fnhe_lock. RCU alone prevents reclamation, but would still allow concurrent writers to leave a mixed pair. Walk the table under RCU and acquire fnhe_lock only while updating each exception. RCU keeps the current entry alive while the short critical section serializes its paired PMTU fields. This avoids holding the global lock while scanning all 2048 buckets for every nexthop.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

