CVE-2026-64047 net: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring
An off-by-one error in Linux kernel TLS handling can lead to memory corruption, potentially causing denial of service or code execution.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64047?
CVE-2026-64047 is a critical vulnerability in Linux kernel, published on 19 Jul 2026. 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:
net: tls: fix off-by-one in sg_chain entry count for wrapped sk_msg ring
When an sk_msg scatterlist ring wraps (sg.end < sg.start), tls_push_record() chains the tail portion of the ring to the head using sg_chain(). An extra entry in the sg array is reserved for this:
struct sk_msg_sg { [...] /* The extra two elements: * 1) used for chaining the front and sections when the list becomes * partitioned (e.g. end < start). The crypto APIs require the * chaining; * 2) to chain tailer SG entries after the message. */ struct scatterlist data[MAX_MSG_FRAGS + 2];
The current code uses MAX_SKB_FRAGS + 1 as the ring size:
sg_chain(&msg_pl->sg.data[msg_pl->sg.start], MAX_SKB_FRAGS - msg_pl->sg.start + 1, msg_pl->sg.data);
This places the chain pointer at
sg_chain(data[start], (MAX_SKB_FRAGS - msg_start + 1) .. = &data[start] + (MAX_SKB_FRAGS - msg_start + 1) - 1 = data[start + (MAX_SKB_FRAGS - start + 1) - 1] = data[MAX_SKB_FRAGS]
instead of the true last entry. This is likely due to a "race" of the commit under Fixes landing close to commit 031097d9e079 ("bpf: sk_msg, zap ingress queue on psock down")
Convert to ARRAY_SIZE and drop the data[start] / - start (as suggested by Sabrina).
Which versions are affected by CVE-2026-64047?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64047?
Apply the vendor's patch.
Is CVE-2026-64047 being exploited?
There is no known exploitation of CVE-2026-64047 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64047, DEBIAN-CVE-2026-64047, GHSA-25cm-2563-466g, UBUNTU-CVE-2026-64047.