high CVSS 7.1

CVE-2024-35939·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: dma-direct: Leak pages on dma_set_decrypted() failure On TDX it is possible for the untrusted host to cause set_memory_encrypted() or set_memory_decrypted() to fail such that an error is returned and the resulting memory is shared. Callers need to take care to handle these errors to avoid returning decrypted (shared) memory to the page allocator, which could lead to functional or security issues. DMA could free decrypted/shared pages if dma_set_decrypted() fails. This should be a rare case. Just leak the pages in this case instead of freeing them.

Severity
high
Software
Kernel
Fixed in
6.8.6
Published
2024-05-19

Affected versions

From: 6.7

Until: 6.8.6

Fixed in: 6.8.6

How to fix this CVE

Update your Linux kernel to version 6.8.6 or later to fix this DMA memory management vulnerability. This patch prevents the kernel from returning decrypted shared memory pages to the allocator when encryption state changes fail, avoiding potential security and stability issues. Apply the update immediately using your distribution's package manager.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your kernel version with `uname -r` and compare against 6.8.6. If version is 6.7.x through 6.8.5, your system is vulnerable.
  2. Step 2: Verify if DMA operations are active on your system by checking `/proc/iomem` and `/proc/ioports` for device mappings; TDX-enabled systems are at higher risk.
  3. Step 3: Monitor kernel logs with `sudo journalctl -k -p err` for messages containing 'set_memory_decrypted' or 'dma_direct' failures, which indicate exploitation attempts.
  4. Step 4: After patching, confirm the new kernel version with `uname -r` and verify it shows 6.8.6 or later, then reboot if necessary.

FAQ

What is CVE-2024-35939?

This vulnerability affects the Linux kernel's DMA direct memory access handling, where a failure in decrypting shared memory could leave pages in an unsafe state and return them to the allocator, potentially causing security or functionality issues in systems using TDX (Trusted Domain Extensions).

Is CVE-2024-35939 being actively exploited?

No, this vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog and no public exploits are currently available, though it remains a high-severity issue requiring prompt patching.

What versions of Kernel are affected by CVE-2024-35939?

Linux kernel versions 6.7 through 6.8.5 are vulnerable. The vulnerability was patched in version 6.8.6 and later stable releases.

How do I check if my server is vulnerable to CVE-2024-35939?

Run `uname -r` to check your kernel version. If it displays a version between 6.7 and 6.8.5, your system is vulnerable. Additionally, check if TDX is enabled with `grep -i tdx /proc/cpuinfo` or `dmesg | grep -i tdx`.

Does Defensia detect CVE-2024-35939?

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-2024-35939 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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