medium CVSS 6.3

CVE-2024-38544·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: Fix seg fault in rxe_comp_queue_pkt In rxe_comp_queue_pkt() an incoming response packet skb is enqueued to the resp_pkts queue and then a decision is made whether to run the completer task inline or schedule it. Finally the skb is dereferenced to bump a 'hw' performance counter. This is wrong because if the completer task is already running in a separate thread it may have already processed the skb and freed it which can cause a seg fault. This has been observed infrequently in testing at high scale. This patch fixes this by changing the order of enqueuing the packet until after the counter is accessed.

Severity
medium
Software
Kernel
Fixed in
6.9.3
Published
2024-06-19

Affected versions

From: 6.9

Until: 6.9.3

Fixed in: 6.9.3

How to fix this CVE

Update your Linux kernel to version 6.9.3 or later to resolve a race condition in the RDMA/rxe driver that can cause kernel segmentation faults. This vulnerability occurs when packet processing overlaps between threads, leading to use-after-free conditions. Apply the patch immediately on systems using kernel 6.9 through 6.9.2, particularly those with high-scale RDMA workloads.

sudo dnf update kernel kernel-devel kernel-headers

Defensia detects this vulnerability

How to check if you are affected

  1. Run `uname -r` to check your current kernel version; if it reports 6.9.0, 6.9.1, or 6.9.2, your system is vulnerable
  2. Check if RDMA/rxe driver is loaded with `lsmod | grep rdma` or `lsmod | grep rxe`; if present, the vulnerability surface is active
  3. Search kernel logs for segmentation faults related to rxe_comp_queue_pkt: `sudo dmesg | grep -i 'seg fault\|rxe_comp\|unable to handle kernel'`
  4. Verify the fix by confirming kernel version is 6.9.3 or later with `uname -r`, and check that no new kernel panic messages appear in `sudo journalctl -u kernel -n 50`

FAQ

What is CVE-2024-38544?

CVE-2024-38544 is a race condition in the Linux kernel's RDMA/rxe driver where a packet buffer may be dereferenced after being freed by a concurrent thread, causing kernel crashes. The vulnerability exists in the rxe_comp_queue_pkt() function where packet enqueueing and counter access operations were not properly sequenced.

Is CVE-2024-38544 being actively exploited?

No, CVE-2024-38544 is not listed as actively exploited by CISA and no public exploits are available. This is a reliability/stability issue rather than a security vulnerability that would allow unauthorized access or privilege escalation.

What versions of Kernel are affected by CVE-2024-38544?

Linux kernel versions 6.9.0 through 6.9.2 are vulnerable. The fix is included in kernel 6.9.3 and later stable releases.

How do I check if my server is vulnerable to CVE-2024-38544?

Run `uname -r` to see your kernel version. If it returns 6.9.0, 6.9.1, or 6.9.2 and you have RDMA/rxe in use, verify with `lsmod | grep rxe` or `ethtool -i ethX` to confirm RDMA interface presence.

Does Defensia detect CVE-2024-38544?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Linux kernel is installed on a monitored server, CVE-2024-38544 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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