CVE-2025-39848: Debian Linux

Medium severity, CVSS 5.5. EPSS: 0.2% chance of exploitation in the next 30 days.

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()").

Affected products

• Debian Debian Linux: version 11.0 only
• Linux Linux Kernel: from 2.6.12.1, before 5.4.299 (fixed in 5.4.299); from 5.5, before 5.10.243 (fixed in 5.10.243); from 5.11, before 5.15.192 (fixed in 5.15.192); from 5.16, before 6.1.151 (fixed in 6.1.151); from 6.2, before 6.6.105 (fixed in 6.6.105); from 6.7, before 6.12.46 (fixed in 6.12.46); …

Published 2025-09-19. Last modified 2026-07-30.