CVE-2026-53248 Overview
CVE-2026-53248 is a use-after-free vulnerability in the Linux kernel's Airoha network driver. The flaw resides in the airoha_metadata_dst_free() function, which invokes metadata_dst_free() to release a metadata_dst structure using kfree() directly. This call path bypasses the Read-Copy-Update (RCU) grace period required by readers in the receive path.
In the RX path, skb_dst_set_noref() stores a non-refcounted pointer from the socket buffer (skb) to the metadata_dst. When the driver tears down the destination while concurrent RCU readers still hold the noref pointer, freed memory can be accessed.
Critical Impact
Concurrent RCU readers may dereference freed metadata_dst memory during driver teardown, leading to kernel memory corruption or denial of service.
Affected Products
- Linux kernel versions containing the Airoha Ethernet driver prior to the fix commits
- Stable kernel branches referenced by commits 4b5a574, 6f829e2, and b38cae8
- Systems using Airoha network hardware with the affected driver
Discovery Timeline
- 2026-06-25 - CVE-2026-53248 published to NVD
- 2026-06-25 - Last updated in NVD database
Technical Details for CVE-2026-53248
Vulnerability Analysis
The vulnerability is a [CWE-416] use-after-free condition in the Airoha network driver's destination metadata teardown logic. The Linux kernel uses metadata_dst objects to carry tunnel and per-packet metadata alongside socket buffers. To minimize reference-count contention in hot RX paths, drivers commonly attach these structures using skb_dst_set_noref(), which sets a non-refcounted pointer that is only valid inside an RCU read-side critical section.
The Airoha driver's airoha_metadata_dst_free() calls metadata_dst_free(), which immediately invokes kfree() on the metadata object. Because skbs in flight may still reference the structure without holding a refcount, freeing the memory synchronously violates the RCU contract enforced by the noref API.
The upstream fix replaces metadata_dst_free() with dst_release(). When the destination's refcount drops to zero, dst_release() schedules the actual free via call_rcu_hurry(), guaranteeing all RCU readers complete before the memory is reclaimed.
Root Cause
The root cause is a mismatch between the allocation lifecycle assumed by skb_dst_set_noref() and the synchronous free performed by metadata_dst_free(). The noref pattern requires deferred reclamation via RCU, but the teardown path skipped the grace period entirely.
Attack Vector
Triggering the condition requires racing driver teardown or reconfiguration against active RX traffic on an interface using the Airoha driver. The vulnerability is not remotely exploitable in the traditional sense and requires local conditions on systems running the affected driver.
No verified proof-of-concept code is publicly available. See the Kernel Git Commit 4b5a574, Kernel Git Commit 6f829e2, and Kernel Git Commit b38cae8 for the authoritative source-level fix.
Detection Methods for CVE-2026-53248
Indicators of Compromise
- Kernel oops or panic messages referencing metadata_dst, skb_dst, or the Airoha driver during interface teardown or reconfiguration
- KASAN (Kernel Address Sanitizer) reports flagging use-after-free in metadata_dst_free() call chains
- Unexplained network driver crashes correlated with link state changes on Airoha-equipped hardware
Detection Strategies
- Enable KASAN on test kernels to surface use-after-free conditions during driver stress and teardown testing
- Audit installed kernel versions against the fix commits referenced in the upstream stable tree
- Monitor kernel ring buffer logs (dmesg) for soft lockups or memory corruption signatures involving network destinations
Monitoring Recommendations
- Centralize kernel logs from Linux endpoints and alert on panic strings tied to network driver subsystems
- Track kernel build versions across the fleet and flag hosts running pre-patch kernels with Airoha hardware
- Correlate interface flap events with subsequent kernel instability on affected platforms
How to Mitigate CVE-2026-53248
Immediate Actions Required
- Identify Linux hosts running the Airoha Ethernet driver and prioritize them for kernel updates
- Apply the upstream stable kernel containing commits 4b5a574e033e, 6f829e2c17a5, and b38cae85d1c4
- Restrict local access to systems pending patch deployment to reduce opportunities to trigger teardown races
Patch Information
The fix replaces the synchronous metadata_dst_free() call with dst_release(), routing the free through the refcount path and call_rcu_hurry() so that RCU readers complete before memory is reclaimed. Patches are available in the upstream stable tree via Kernel Git Commit 4b5a574, Kernel Git Commit 6f829e2, and Kernel Git Commit b38cae8.
Workarounds
- Avoid driver reload, interface bring-down, or device removal operations on affected hardware while RX traffic is active
- Where feasible, disable or unload the Airoha driver on hosts that do not require it until patched kernels are deployed
- Limit administrative shell access to trusted operators to reduce the chance of triggering teardown sequences under load
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
