CVE-2023-53333 netfilter: conntrack: dccp: copy entire header to stack buffer, not just basic one
A stack-out-of-bounds read in the Linux kernel's DCCP conntrack module allows attackers to cause a denial of service or leak sensitive memory information.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-53333?
CVE-2023-53333 is a high-severity memory corruption vulnerability in Linux kernel, published on 16 Sep 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: conntrack: dccp: copy entire header to stack buffer, not just basic one
Eric Dumazet says: nf_conntrack_dccp_packet() has an unique:
dh = skb_header_pointer(skb, dataoff, sizeof(_dh), &_dh);
And nothing more is 'pulled' from the packet, depending on the content. dh->dccph_doff, and/or dh->dccph_x ...) So dccp_ack_seq() is happily reading stuff past the _dh buffer.
BUG: KASAN: stack-out-of-bounds in nf_conntrack_dccp_packet+0x1134/0x11c0 Read of size 4 at addr ffff000128f66e0c by task syz-executor.2/29371 [..]
Fix this by increasing the stack buffer to also include room for the extra sequence numbers and all the known dccp packet type headers, then pull again after the initial validation of the basic header.
While at it, mark packets invalid that lack 48bit sequence bit but where RFC says the type MUST use them.
Compile tested only.
v2: first skb_header_pointer() now needs to adjust the size to only pull the generic header. (Eric)
Heads-up: I intend to remove dccp conntrack support later this year.
Weakness: CWE-125
Which versions are affected by CVE-2023-53333?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2023-53333?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2023-53333 being exploited?
There is no known exploitation of CVE-2023-53333 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2023-53333, DEBIAN-CVE-2023-53333, GHSA-r2m9-j67m-7grm, UBUNTU-CVE-2023-53333.