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CVE-2026-80603
netfilter: nf_conntrack_irc: fix parse_dcc() off-by-one OOB read
Published 2026-08-28 (2 months ago) by the Linux kernel CNA. Subsystem net/netfilter. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-80603 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/netfilter/nf_conntrack_irc.c
- What this is
- NETFILTERMAINTAINERS section matched on net/netfilter/ · netfilter-devel@vger.kernel.org · Maintained
- Kernel module
- nf_conntrack_irc
Check it on the machine
grep -wE 'CONFIG_NETFILTER|CONFIG_NF_CONNTRACK_IRC' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w nf_conntrack_ircPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switches
- CONFIG_NETFILTER, CONFIG_NF_CONNTRACK_IRC
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-28 (2 months ago)source
- CVSS
- 9.1 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.60%, higher than 47.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/netfilter
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.12 | 5.10.261 | abb8c32b88ea |
| 2.6.12 | 5.15.212 | 437e0a3854b3 |
| 2.6.12 | 6.1.178 | 910c33e4a8c0 |
| 2.6.12 | 6.6.145 | 2b70f61f569b |
| 2.6.12 | 6.12.97 | 2393f0bd7a46 |
| 2.6.12 | 6.18.40 | aff589556ed7 |
| 2.6.12 | 7.1.5 | eeef3b81f449 |
| 2.6.12 | 7.2 | ef6400ca25a1 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The bug is reached from attacker-controlled TCP payloads on IPv4 flows processed by nf_confirm() (POST_ROUTING/LOCAL_IN) when the IRC conntrack helper is attached, e.g. on an IRC-exposed host or NAT/firewall handling IRC/DCC through netfilter.
- AC:LAttack complexity, low
- Once the IRC helper is active on a tracked flow, exploitation is deterministic: the attacker completes a TCP handshake, sends a crafted client-to-server PRIVMSG/CTCP DCC without a newline at the copy boundary, and can plant the stale byte via the shared global irc_buffer.
- PR:NPrivileges required, none
- No local account or kernel capabilities are required; a remote peer only needs to send network traffic on a connection where the administrator has enabled the IRC helper. Helper configuration is deployment state, not attacker privilege.
- UI:NUser interaction, none
- No victim-side clicks, mounts, or other interactive actions are needed beyond normal network reachability; the attacker supplies the malicious IRC/DCC payload directly over the established TCP session.
- S:UScope, unchanged
- Impact is confined to the kernel/netfilter security domain of the affected host (conntrack parsing and expectations). It does not cross VM, IOMMU, or other separate security-authority boundaries.
- C:HConfidentiality impact, high
- parse_dcc() performs a one-byte out-of-bounds read past skb_header_pointer()'s copied region into stale kmalloc data in the shared irc_buffer, exposing uninitialized or prior-session bytes that can influence subsequent parsing.
- I:HIntegrity impact, high
- If the overread byte is an ASCII digit, simple_strtoul() misparses the DCC address/port and can install incorrect nf_conntrack expectations, altering NAT/firewall pinholes rather than only reading memory.
- A:NAvailability impact, none
- The overread is bounded by the deliberately oversized kmalloc guard (MAX_SEARCH_SIZE+1) and the fix commit states the stray access does not fault; this issue does not directly cause kernel oops, panic, or hang.