CVE-2026-72391 net: phy: sfp: free mii_bus in sfp_i2c_mdiobus_destroy
A memory leak in the Linux kernel SFP driver allows attackers to cause denial of service by repeatedly removing copper SFP modules.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72391?
CVE-2026-72391 is a memory corruption vulnerability in Linux, published on 15 Aug 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:
net: phy: sfp: free mii_bus in sfp_i2c_mdiobus_destroy
sfp_i2c_mdiobus_create() allocates the I2C MDIO bus with mdio_i2c_alloc(), a plain (non-devm) allocation, and registers it. sfp_i2c_mdiobus_destroy() only unregisters the bus and clears sfp->i2c_mii without calling mdiobus_free(). As the only reference to the bus is then cleared, the struct mii_bus is leaked.
This is hit whenever a copper/RollBall SFP module that instantiated an MDIO bus is removed: sfp_sm_main() takes the global teardown path and calls sfp_i2c_mdiobus_destroy(). sfp_cleanup(), on driver unbind, frees sfp->i2c_mii directly, which is why the leak only triggered on module hot-removal and not on unbind.
Free the bus in sfp_i2c_mdiobus_destroy() to match the allocation done in sfp_i2c_mdiobus_create().
Which versions are affected by CVE-2026-72391?
How do I fix CVE-2026-72391?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-72391 being exploited?
There is no known exploitation of CVE-2026-72391 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72391, DEBIAN-CVE-2026-72391, GHSA-j3vv-g378-r9j2, UBUNTU-CVE-2026-72391.