CVE-2025-39847 ppp: fix memory leak in pad_compress_skb
A memory leak in the Linux kernel PPP module allows attackers to cause denial of service by exhausting system memory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39847?
CVE-2025-39847 is a medium-severity denial of service 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:
ppp: fix memory leak in pad_compress_skb
If alloc_skb() fails in pad_compress_skb(), it returns NULL without releasing the old skb. The caller does:
skb = pad_compress_skb(ppp, skb); if (!skb) goto drop;
drop: kfree_skb(skb);
When pad_compress_skb() returns NULL, the reference to the old skb is lost and kfree_skb(skb) ends up doing nothing, leading to a memory leak.
Align pad_compress_skb() semantics with realloc(): only free the old skb if allocation and compression succeed. At the call site, use the new_skb variable so the original skb is not lost when pad_compress_skb() fails.
Weakness: CWE-401
Which versions are affected by CVE-2025-39847?
It affects 2 products.
Products include Debian Debian Linux, Linux kernel.
How do I fix CVE-2025-39847?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-39847 being exploited?
There is no known exploitation of CVE-2025-39847 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as AZL-67553, AZL-74841, BELL-CVE-2025-39847, DEBIAN-CVE-2025-39847, GHSA-9f6g-j2jq-6w3f, ROOT-OS-DEBIAN-11-CVE-2025-39847 and 5 more.