CVE-2026-68156 libceph: refresh auth->authorizer_buf{,_len} after authorizer update
A use-after-free in the Linux kernel Ceph client allows attackers to trigger memory corruption or crashes during messenger reconnections.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68156?
CVE-2026-68156 is a critical use after free vulnerability in Linux, published on 10 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
libceph: refresh auth->authorizer_buf{,_len} after authorizer update
ceph_x_create_authorizer() caches au->buf->vec.iov_base and au->buf->vec.iov_len in struct ceph_auth_handshake. These cached values are then used by the messenger connect code when sending the authorizer.
ceph_x_update_authorizer() can rebuild the authorizer when a newer service ticket is available. If the rebuilt authorizer no longer fits in the existing buffer, ceph_x_build_authorizer() drops its reference to au->buf and allocates a new one. If this is the final reference, ceph_buffer_put() frees the old ceph_buffer and its vec.iov_base, but auth->authorizer_buf still points at that freed memory.
A subsequent msgr1 reconnect can therefore queue the stale pointer and trigger a KASAN slab-use-after-free in _copy_from_iter() while tcp_sendmsg() copies the authorizer.
Refresh auth->authorizer_buf and auth->authorizer_buf_len after a successful authorizer rebuild so the messenger sends the current buffer.
Weakness: CWE-416
Which versions are affected by CVE-2026-68156?
How do I fix CVE-2026-68156?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-68156 being exploited?
There is no known exploitation of CVE-2026-68156 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68156, DEBIAN-CVE-2026-68156, GHSA-rf74-56p2-8jqj, UBUNTU-CVE-2026-68156.