high CVSS 7.8

CVE-2024-56626·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix Out-of-Bounds Write in ksmbd_vfs_stream_write An offset from client could be a negative value, It could allows to write data outside the bounds of the allocated buffer. Note that this issue is coming when setting 'vfs objects = streams_xattr parameter' in ksmbd.conf.

Severity
high
Software
Kernel
Fixed in
6.12.5
Published
2024-12-27

Affected versions

From: 6.7

Until: 6.12.5

Fixed in: 6.12.5

How to fix this CVE

Update your Linux kernel to version 6.12.5 or later to patch the out-of-bounds write vulnerability in ksmbd's stream handling. This fix is critical if you have configured the 'vfs objects = streams_xattr' parameter in your ksmbd.conf file, as the vulnerability allows negative offsets from clients to write beyond allocated buffer boundaries. Ensure you test the kernel update in a non-production environment before deploying to production systems.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r — verify it is at least 6.12.5
  2. Verify if ksmbd is running: systemctl status ksmbd or ps aux | grep ksmbd
  3. Check if streams_xattr is enabled: grep 'vfs objects.*streams_xattr' /etc/ksmbd/ksmbd.conf
  4. Confirm the fix: grep -i 'stream_write\|offset' /var/log/kern.log | tail -20 to review recent kernel messages related to stream handling

FAQ

What is CVE-2024-56626?

This vulnerability exists in the Linux kernel's ksmbd SMB server implementation, where negative offset values sent by clients can bypass buffer bounds checks during stream write operations, leading to memory corruption with high integrity and confidentiality impact.

Is CVE-2024-56626 being actively exploited?

No, CVE-2024-56626 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are currently available.

What versions of Kernel are affected by CVE-2024-56626?

Linux kernel versions 6.7 through 6.12.4 are vulnerable; the fix is available in kernel 6.12.5 and later.

How do I check if my server is vulnerable to CVE-2024-56626?

Run 'uname -r' to check your kernel version — if it is between 6.7 and 6.12.4 AND you have 'vfs objects = streams_xattr' configured in ksmbd.conf, your system is vulnerable.

Does Defensia detect CVE-2024-56626?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2024-56626 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-64355CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: bpf: Reject fragmented frames in devmap Devmap broadcast redirects clone the packet for all but the last destination. For native XDP, that clone path copies only the linear xdp_frame data, while fragmented frames keep skb_shared_info in tailroom outside the linear area. Cloning such a frame leaves XDP_FLAGS_HAS_FRAGS set but without valid frag metadata, and the later free path can interpret uninitialized tail data as skb_shared_info, leading to an out-of-bounds access during frame return. Reject fragmented native XDP frames in dev_map_enqueue_clone(). Add the same restriction to the generic XDP clone path in dev_map_redirect_clone(). Generic XDP represents fragmented packets as nonlinear skbs, and rejecting them here keeps clone-based broadcast support aligned between native and generic XDP.
CVE-2026-63993CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.
CVE-2026-43501CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows ipv6_rpl_srh_rcv() decompresses an RFC 6554 Source Routing Header, swaps the next segment into ipv6_hdr->daddr, recompresses, then pulls the old header and pushes the new one plus the IPv6 header back. The recompressed header can be larger than the received one when the swap reduces the common-prefix length the segments share with daddr (CmprI=0, CmprE>0, seg[0][0] != daddr[0] gives the maximum +8 bytes). pskb_expand_head() was gated on segments_left == 0, so on earlier segments the push consumed unchecked headroom. Once skb_push() leaves fewer than skb->mac_len bytes in front of data, skb_mac_header_rebuild()'s call to: skb_set_mac_header(skb, -skb->mac_len); will store (data - head) - mac_len into the u16 mac_header field, which wraps to ~65530, and the following memmove() writes mac_len bytes ~64KiB past skb->head. A single AF_INET6/SOCK_RAW/IPV6_HDRINCL packet over lo with a two segment type-3 SRH (CmprI=0, CmprE=15) reaches headroom 8 after one pass; KASAN reports a 14-byte OOB write in ipv6_rthdr_rcv. Fix this by expanding the head whenever the remaining room is less than the push size plus mac_len, and request that much extra so the rebuilt MAC header fits afterwards.
CVE-2026-64216CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages() netfs_unlock_abandoned_read_pages(rreq) accesses the index of the folios it is wanting to unlock and compares that to rreq->no_unlock_folio so that it doesn't unlock a folio being read for netfs_perform_write() or netfs_write_begin(). However, given that netfs_unlock_abandoned_read_pages() is called _after_ NETFS_RREQ_IN_PROGRESS is cleared, the one folio that it's not allowed to dereference is the one specified by ->no_unlock_folio as ownership immediately reverts to the caller. Fix this by storing the folio pointer instead and using that rather than the index. Also fix netfs_unlock_read_folio() where the same applies.

References

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