Look up another CVE · open CVE-2026-68119 in the interactive tracker
CVE-2026-68119
tcp: initialize standalone TCP-AO response padding
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-68119 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
tcp_v4_send_ack() and tcp_v6_send_response() construct standalone TCP responses with TCP-AO options. The option length carries the actual MAC length, but the TCP header length includes the option rounded up to a four-byte boundary. tcp_ao_hash_hdr() writes the MAC only. Thus, when the MAC length is not four-byte aligned, the one to three bytes after the MAC are left uninitialized and may be transmitted. For the normal TCP-AO hashing mode, those bytes also have to be initialized before computing the MAC. Initialize only the alignment padding in the TCP-AO branches, before hashing the header. Use TCPOPT_NOP, as in the normal TCP-AO output path. This avoids adding work to non-AO TCP responses while preserving a valid authenticated header.
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/ipv4/tcp_ipv4.c
net/ipv6/tcp_ipv6.c
- What this is
- NETWORKING [TCP]MAINTAINERS section matched on net/ipv4/tcp*.c · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_INET /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.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_INET
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
- 2026-08-10 (2 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:Nsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.37%, higher than 29.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/ipv4
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.7 | 6.12.101 | bbb7db8c74b0 |
| 6.7 | 6.18.42 | fadaff3f66e1 |
| 6.7 | 7.1.6 | a859b280441f |
| 6.7 | 7.2 | e1a9d3cc1182 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | tracker |
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
- Remote attackers reach tcp_v4_send_ack() and tcp_v6_send_response() by sending IPv4/IPv6 TCP segments into tcp_v4_rcv()/tcp_v6_rcv() SYN-RECV, TIME-WAIT, and reset paths that build standalone TCP-AO-signed ACK/RST replies transmitted back over the network.
- AC:LAttack complexity, low
- On Internet-facing TCP-AO deployments (BGP/route-server successors to TCP-MD5), an attacker reliably elicits qualifying standalone responses by sending crafted TCP segments; no race, timing lottery, or uncontrollable memory layout is required beyond the peer using a non-4-byte-aligned MAC length.
- PR:NPrivileges required, none
- The uninitialized bytes are returned to the remote packet sender in standalone TCP-AO ACK/RST replies; triggering requires only network reachability to a TCP-AO-enabled listener or an existing TCP-AO TIME-WAIT socket, with no local credentials on the victim host.
- UI:NUser interaction, none
- No end-user action is needed beyond normal exposure of a TCP-AO-protected network service; the attacker alone sends the triggering TCP segments and captures the padded replies.
- S:UScope, unchanged
- Kernel stack or skb memory is disclosed to a remote TCP peer within the same host kernel security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary scope change.
- C:HConfidentiality impact, high
- One to three uninitialized bytes in TCP-AO option alignment padding from the on-stack IPv4 response buffer or IPv6 skb head are transmitted on every qualifying standalone ACK/RST and can be harvested repeatedly to recover kernel stack or skb contents.
- I:NIntegrity impact, none
- The bug only fails to initialize alignment padding before transmission; it does not write to or corrupt kernel, socket, or application memory.
- A:NAvailability impact, none
- Standalone TCP-AO responses are still transmitted successfully with no kernel oops, panic, hang, or denial of service; only confidentiality of the leaked padding bytes is affected.