CVE-2025-39848 ax25: properly unshare skbs in ax25_kiss_rcv()
A null pointer dereference in the Linux kernel AX.25 module allows attackers to cause a system crash via crafted network packets.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39848?
CVE-2025-39848 is a high-severity vulnerability in Debian Debian Linux, published on 19 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ax25: properly unshare skbs in ax25_kiss_rcv()
Bernard Pidoux reported a regression apparently caused by commit c353e8983e0d ("net: introduce per netns packet chains").
skb->dev becomes NULL and we crash in __netif_receive_skb_core().
Before above commit, different kind of bugs or corruptions could happen without a major crash.
But the root cause is that ax25_kiss_rcv() can queue/mangle input skb without checking if this skb is shared or not.
Many thanks to Bernard Pidoux for his help, diagnosis and tests.
We had a similar issue years ago fixed with commit 7aaed57c5c28 ("phonet: properly unshare skbs in phonet_rcv()").
Weakness: CWE-401
Which versions are affected by CVE-2025-39848?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-39848?
Apply the vendor's patch.
Is CVE-2025-39848 being exploited?
There is no known exploitation of CVE-2025-39848 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-67589, BELL-CVE-2025-39848, DEBIAN-CVE-2025-39848, GHSA-c6g6-j52p-pg8h, ROOT-OS-DEBIAN-11-CVE-2025-39848, ROOT-OS-DEBIAN-12-CVE-2025-39848 and 4 more.