high CVSS 7.8 EPSS <0.1%

CVE-2024-39496·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: btrfs: zoned: fix use-after-free due to race with dev replace While loading a zone's info during creation of a block group, we can race with a device replace operation and then trigger a use-after-free on the device that was just replaced (source device of the replace operation). This happens because at btrfs_load_zone_info() we extract a device from the chunk map into a local variable and then use the device while not under the protection of the device replace rwsem. So if there's a device replace operation happening when we extract the device and that device is the source of the replace operation, we will trigger a use-after-free if before we finish using the device the replace operation finishes and frees the device. Fix this by enlarging the critical section under the protection of the device replace rwsem so that all uses of the device are done inside the critical section.

Severity
high
Software
Kernel
Fixed in
6.9.6
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 3% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2024-39496 scores 7.8 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.7

Until: 6.9.6

Fixed in: 6.9.6

How to fix this CVE

Update your Linux kernel to version 6.9.6 or later to resolve this use-after-free vulnerability in the Btrfs zoned storage subsystem. The vulnerability occurs when device replacement operations race with zone information loading, potentially causing kernel memory corruption. Apply the kernel update and reboot your system to activate the patched version.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your running kernel version with: uname -r — if the version is between 6.7 and 6.9.5 (inclusive), your system is potentially vulnerable.
  2. Verify Btrfs is in use: mount | grep btrfs — if Btrfs filesystems are mounted, this CVE is relevant to your system.
  3. Check kernel configuration for Btrfs zoned support: grep CONFIG_BLK_DEV_ZONED /boot/config-$(uname -r) — if set to 'y', the vulnerable code path may be active.
  4. After applying the kernel update, reboot and verify the new version: uname -r — confirm the kernel version is 6.9.6 or higher.

FAQ

What is CVE-2024-39496?

CVE-2024-39496 is a use-after-free vulnerability in the Linux kernel's Btrfs zoned storage implementation. It occurs when a device replacement operation races with zone information loading, potentially freeing device memory while it is still being accessed, leading to kernel memory corruption or crash.

Is CVE-2024-39496 being actively exploited?

No, CVE-2024-39496 is not listed on the CISA KEV catalog and has no publicly available exploits. However, the high CVSS score (7.8) and local privilege requirement indicate this should still be prioritized for patching.

What versions of Kernel are affected by CVE-2024-39496?

Linux kernel versions 6.7 through 6.9.5 are affected. The vulnerability was resolved in kernel version 6.9.6 and later.

How do I check if my server is vulnerable to CVE-2024-39496?

Run 'uname -r' to check your kernel version — if it falls between 6.7 and 6.9.5, and you use Btrfs with zoned storage devices, your system is vulnerable. Run 'mount | grep btrfs' to confirm Btrfs is in use.

Does Defensia detect CVE-2024-39496?

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-2024-39496 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-53151CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix the ACK parser to extract the SACK table for parsing Fix modification of the received skbuff in rxrpc_input_soft_acks() and a potential incorrect access of the buffer in a fragmented UDP packet (the packet would probably have to be deliberately pre-generated as fragmented) when AF_RXRPC tries to extract the contents of the SACK table by copying out the contents of the SACK table into a buffer before attempting to parse AF_RXRPC assumes that it can just call skb_condense() and then validly access the SACK table from skb->data and that it will be a flat buffer - but skb_condense() can silently fail to do anything under some circumstances. Note that whilst rxrpc_input_soft_acks() should be able to parse extended ACKs, the rest of AF_RXRPC doesn't currently support that. Further, there's then no need to call skb_condense() in rxrpc_input_ack(), so don't.
CVE-2026-53088CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: bcmgenet: fix off-by-one in bcmgenet_put_txcb The write_ptr points to the next open tx_cb. We want to return the tx_cb that gets rewinded, so we must rewind the pointer first then return the tx_cb that it points to. That way the txcb can be correctly cleaned up.
CVE-2026-53228CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sit: reload inner IPv6 header after GSO offloads ipip6_tunnel_xmit() caches the inner IPv6 header pointer at function entry and continues using it after iptunnel_handle_offloads(). For GSO skbs, iptunnel_handle_offloads() calls skb_header_unclone(). When the skb header is cloned, skb_header_unclone() can call pskb_expand_head(), which may move the skb head. The pskb_expand_head() contract requires pointers into the skb header to be reloaded after the call. If the later skb_realloc_headroom() branch is not taken, SIT uses the stale iph6 pointer to read the inner hop limit and DS field. That can read from a freed skb head after the old head's remaining clone is released. Reload iph6 after the offload helper succeeds and before subsequent reads from the inner IPv6 header. Keep the existing reload after skb_realloc_headroom(), since that branch can also replace the skb.

References

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