If this requires a multi-core system to exploit, it's good news for most of the consumer routers that will never get updates. Saved by cheap single-core hardware.
An entire ecosystem of malware crawling and cohabiting in them.
Heck, apparently even the new Unifi UCG Fiber is running 5.4.213 (September 2022), but maybe they backport some fixes?
[1] https://community.ui.com/releases/dd0283dc-bf71-4140-ae1d-c1...
This is wild. I'm a firmware nerd, not a backend nerd, what percentage of TCP/IP servers are 'multipath'?
Also, since IPv6 isn't affected, wouldn't it be funny if this is what it took to get everyone to switch.
Every Ubuntu version in the last decade is currently vulnerable.
https://ubuntu.com/security/CVE-2026-98432
Patches not yet available. That makes this a big deal.
This article says that this isn’t app level but is level and can be exploited before requests reach apps.
I was talking about the Anthropic blog post, only Go/Caddy enable multipath TCP listeners by default.
Why it's urgent: the bug sits in code every Linux server runs when it accepts an IPv4 TCP connection, before any application sees the connection.
It reads like it was LLM generated though so who knows. There is at least a simple mitigation for Golang apps if that is the only concern.
It's an extension to TCP that, similar to QUIC, allows you to use multiple address/port pairs to transmit data over a single logical stream. Both client/initiator and server/listener have to opt into the extension. This might need to be enabled explicitly by the application[1], which Go apparently does for you, or judging from other posts may be enabled by default systemwide, depending on your platform.
AFAIU, a major user of MPTCP is Apple and the iPhone, and the ubiquity of iPhone clients motivated implementation in and deployment on Linux servers.
[1] https://docs.kernel.org/networking/mptcp.html#sockets-api
https://forum.proxmox.com/threads/cve-2026-98432-in-proxmox-...
> AWS Web Application Firewall, Application Load Balancer, Classic Load Balancer, TLS Listeners on Network Load Balancer, Cloud Front, API Gateway
> Customers using the above services do not receive TCP connections from untrusted sources directly when following best practices. AWS is applying updates to the underlying infrastructure of these services and no immediate customer action is required if you are using these services. We still recommend customers update their self-managed instances behind these services within the next 30 days.
[0]: https://aws.amazon.com/security/security-bulletins/2026-160-...
% uname -a
Linux XXXX 5.15.223 #1 SMP PREEMPT Thu Oct 22 00:03:07 CDT 2026
x86_64 Intel(R) Core(TM) i7-4810MQ CPU @ 2.80GHz GenuineIntel GNU/LinuxThe discourse on this is weird, sounds at times as if these are “because of AI.” These are mostly pre-existing bugs, some very old, and they’ve been lurking. If they all get found we exit the other side more secure and reliable.
- MPTCP is not a requirement, it is a generic use-after-free.
- Exploitability over the internet is unlikely, most ISP routers drop packets with ipoptions fields.
- At least according to Red Hat, dropping packets with ipoptions yourself helps, but is not a full mitigation.
- Successful exploit requires multiple CPU cores to process packets, so systems with just a single core or packet processing pinned to a single core are not affected.
That doesn't track. Apple iPhones are a major user of MPTCP and they report the majority of requests supporting MPTCP, IIRC 70+%.
I ask because I’ve been dabbling in rooting various closed devices at home. I’m finding AI fantastic at finding vulnerabilities statically (from firmware upgrade binaries), but when you then ask it to use it to get root or code execution it just goes in circles.
In the end it usually ends up there’s no exploit it can find, because it can’t actually influence the affected memory in a useful way. This is especially so if that memory is in the heap. On the stack it’s a lot more predictable (especially with OOB writes).
https://www.reddit.com/r/openwrt/comments/1xka85h/is_the_ope...
They say 25.12-SNAPSHOT has it fixed
Anthropic only exploited multipath TCP, but the bug is deeper and also affects TCP connections, but it looks like this path is harder to exploit, and it's unclear if anybody managed to.
no idea, but at least Tailscale and Caddy were opening MPTCP sockets on servers I checked.
Multipath TCP is a neat trick that allows a single TCP connection (TCP = Transport Control Protocol, a stateless protocol for long running connections) to use multiple physical interfaces. You could do something similar before MTCP using bonding, but this was annoying to set up and usually required application level code to efficiently use the bonded connection. MTCP makes this much simpler from an application level point of view and it can use widely diverse underlying transport layers at the same time (for instance, WiFi, Cellular and wired connections).
oger•1h ago
Watch your Linux systems for kernel updates. Reboot!
tgv•26m ago