CVE-2026-98289 af_unix: Unify scc_index when finalising SCC in __unix_walk_scc().
A logic error in the Linux kernel's Unix socket garbage collector can cause memory leaks, leading to denial of service.
- 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-2026-98289?
CVE-2026-98289 is a memory corruption vulnerability in Linux, published on 6 Oct 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:
af_unix: Unify scc_index when finalising SCC in __unix_walk_scc().
Commit bfdb01283ee8 ("af_unix: Assign a unique index to SCC.") changed Tarjan's algorithm to update lowlink with lowlink, which is called lowpoint (unix_vertex.scc_index).
unix_vertex_dead() assumes all vertices in an SCC share the same lowpoint, but this is not always true if an SCC has two or more back edges, depending on the order of DFS.
For example, the graph below has two back edges from B to A and from C to B.
A --> B --> C ^ | ^ | `----' `----'
If DFS walks through A -> B -> C -> B (-> C -> B) -> A (-> B -> A), each index and scc_index will be updated as follows.
A --> B --> C C = (3, 3) (index, scc_index) B = (2, 2) A = (1, 1)
A ... B ... C C = (3, 2)<-. ^ | B = (2, 2) -' `----' A = (1, 1)
A ... B ... C C = (3, 2) ^ | . . B = (2, 1)<-. `----' .... A = (1, 1) -'
Then, unix_vertex_dead() thinks that B is passed to another SCC with scc_index 2, and the SCC is not garbage-collected.
This does not happen if DFS walks in a different order below or starts from B.
1 3 A --> B --> C ^ | ^ | `----' `----' 2 4
Let's unify scc_index across the SCC when finalising it.
Note that updating v->index was previously done in unix_scc_dead(), when called from __unix_walk_scc(), just to save one loop. Since __unix_walk_scc() now iterates over the SCC anyway, the update is moved back to __unix_walk_scc() and 'fast' argument is dropped.
Which versions are affected by CVE-2026-98289?
How do I fix CVE-2026-98289?
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-2026-98289 being exploited?
There is no known exploitation of CVE-2026-98289 in the wild and no public exploit code.
Sources
Also known as AZL-106236, BELL-CVE-2026-98289, DEBIAN-CVE-2026-98289, GHSA-3rq9-mjhw-q3g6, UBUNTU-CVE-2026-98289.