high CVSS 7.8

CVE-2024-26689·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ceph: prevent use-after-free in encode_cap_msg() In fs/ceph/caps.c, in encode_cap_msg(), "use after free" error was caught by KASAN at this line - 'ceph_buffer_get(arg->xattr_buf);'. This implies before the refcount could be increment here, it was freed. In same file, in "handle_cap_grant()" refcount is decremented by this line - 'ceph_buffer_put(ci->i_xattrs.blob);'. It appears that a race occurred and resource was freed by the latter line before the former line could increment it. encode_cap_msg() is called by __send_cap() and __send_cap() is called by ceph_check_caps() after calling __prep_cap(). __prep_cap() is where arg->xattr_buf is assigned to ci->i_xattrs.blob. This is the spot where the refcount must be increased to prevent "use after free" error.

Severity
high
Software
Kernel
Fixed in
6.7.6
Published
2024-04-03

Affected versions

From: 6.7

Until: 6.7.6

Fixed in: 6.7.6

How to fix this CVE

Update your Linux kernel to version 6.7.6 or later to resolve a use-after-free vulnerability in the Ceph filesystem capability messaging code. This race condition could allow local privilege escalation if multiple kernel subsystems access shared buffer resources concurrently. Apply the patch immediately on systems running kernel versions 6.7 through 6.7.5.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Run 'uname -r' to check your current kernel version. If it shows 6.7.0 through 6.7.5, you are vulnerable.
  2. Check if Ceph filesystem is mounted with 'mount | grep ceph'. If present, the vulnerable code path can be triggered.
  3. Search kernel logs for KASAN warnings with 'dmesg | grep -i "use-after-free\|kasan\|ceph"' to detect exploitation attempts.
  4. After patching, verify the new kernel version with 'uname -r' and confirm it is 6.7.6 or later, then reboot if needed.

FAQ

What is CVE-2024-26689?

CVE-2024-26689 is a use-after-free vulnerability in the Linux kernel's Ceph filesystem driver where a reference-counted buffer can be freed by one kernel path while another path attempts to increment its reference count, leading to memory corruption.

Is CVE-2024-26689 being actively exploited?

No, according to CISA's KEV catalog, CVE-2024-26689 is not currently being exploited in the wild, and no public proof-of-concept exploits are available.

What versions of Kernel are affected by CVE-2024-26689?

Linux kernel versions 6.7 through 6.7.5 are affected. Version 6.7.6 and later contain the fix.

How do I check if my server is vulnerable to CVE-2024-26689?

Run 'uname -r' and check if the output is between 6.7 and 6.7.5; also verify Ceph is in use with 'mount | grep ceph' or 'lsmod | grep ceph'.

Does Defensia detect CVE-2024-26689?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2024-26689 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-100075CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters When srpt_alloc_rw_ctxs() fails partway through a multi-buffer indirect descriptor, the unwind path destroys RDMA contexts but leaves stale n_rw_ctx and n_rdma values (and a dangling rw_ctxs pointer). Later sq_wr_avail accounting in srpt_queue_response() or srpt_write_pending() can then subtract the wrong number of send queue credits. Reset the counters and clear rw_ctxs after freeing the heap allocation before returning an error.
CVE-2026-64033CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: RDMA/rtrs: Fix use-after-free in path file creation cleanup In the error path of rtrs_srv_create_path_files(), the sysfs root folders may already have been created and srv_path->kobj may already have been initialized. If a later step fails, the cleanup currently calls kobject_put(&srv_path->kobj) before rtrs_srv_destroy_once_sysfs_root_folders(srv_path). kobject_put() may drop the last reference to srv_path->kobj and invoke the release callback, rtrs_srv_release(), which frees srv_path. The following call to rtrs_srv_destroy_once_sysfs_root_folders(srv_path) then dereferences srv_path internally to access srv_path->srv, resulting in a use-after-free. This failure path is reached before rtrs_srv_create_path_files() returns success, so the successful-path lifetime handling is not involved. Fix this by destroying the sysfs root folders before calling kobject_put(&srv_path->kobj), so srv_path is still valid while the helper accesses it. This issue was found by a static analysis tool I am developing.
CVE-2026-64007CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfilter: synproxy: refresh tcphdr after skb_ensure_writable synproxy_tstamp_adjust() rewrites the TCP timestamp option in place and then patches the TCP checksum via inet_proto_csum_replace4() on the caller-supplied tcphdr pointer. Both ipv4_synproxy_hook() and ipv6_synproxy_hook() obtain that pointer with skb_header_pointer() before calling in, so it may either alias skb->head directly or point at the caller's on-stack _tcph buffer. Between obtaining the pointer and using it, the function calls skb_ensure_writable(skb, optend), which on a cloned or non-linear skb invokes pskb_expand_head() and frees the old skb->head. After that point the cached th is stale: caller (ipv[46]_synproxy_hook) th = skb_header_pointer(skb, ..., &_tcph) synproxy_tstamp_adjust(skb, protoff, th, ...) skb_ensure_writable(skb, optend) pskb_expand_head() /* kfree(old skb->head) */ ... inet_proto_csum_replace4(&th->check, ...) /* writes into freed head, or into the caller's stack copy leaving the on-wire checksum stale */ The option bytes are written through skb->data and are fine; only the checksum update goes through th and so lands in the wrong place. The result is either a write into freed slab memory or a packet leaving with a checksum that does not match its payload. Fix by re-deriving th from skb->data + protoff immediately after skb_ensure_writable() succeeds, so the subsequent checksum update targets the linear, writable header.
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References

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