CVE-2022-49086 net: openvswitch: fix leak of nested actions
A memory leak in the Linux kernel's Open vSwitch module allows attackers to cause denial of service via high-rate flow rotation.
- 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-2022-49086?
CVE-2022-49086 is a medium-severity denial of service vulnerability in Linux kernel, published on 26 Feb 2025. 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: openvswitch: fix leak of nested actions
While parsing user-provided actions, openvswitch module may dynamically allocate memory and store pointers in the internal copy of the actions. So this memory has to be freed while destroying the actions.
Currently there are only two such actions: ct() and set(). However, there are many actions that can hold nested lists of actions and ovs_nla_free_flow_actions() just jumps over them leaking the memory.
For example, removal of the flow with the following actions will lead to a leak of the memory allocated by nf_ct_tmpl_alloc():
actions:clone(ct(commit),0)
Non-freed set() action may also leak the 'dst' structure for the tunnel info including device references.
Under certain conditions with a high rate of flow rotation that may cause significant memory leak problem (2MB per second in reporter's case). The problem is also hard to mitigate, because the user doesn't have direct control over the datapath flows generated by OVS.
Fix that by iterating over all the nested actions and freeing everything that needs to be freed recursively.
New build time assertion should protect us from this problem if new actions will be added in the future.
Unfortunately, openvswitch module doesn't use NLA_F_NESTED, so all attributes has to be explicitly checked. sample() and clone() actions are mixing extra attributes into the user-provided action list. That prevents some code generalization too.
Weakness: CWE-401
Which versions are affected by CVE-2022-49086?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-49086?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-49086 being exploited?
There is no known exploitation of CVE-2022-49086 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-49086, GHSA-jpcv-cqh9-hpf3, UBUNTU-CVE-2022-49086.