Linux’s TCP bug can root Go servers, one ChatGPT link took your account, and HackerTube

On Saturday's HN front page, the story for anyone who runs servers is a use-after-free in Linux's IPv4 TCP handshake. It sits in code every Linux server runs when it accepts a connection, before your application sees anything, and the attacker needs no login. It goes back to Linux 4.4, and it scores near the top of the severity scale. Upstream fixed it with a four-line change, in stable kernels released between October 11 and 15.

Anthropic's Claude wrote a working exploit that runs commands as root, with no credentials, on Linux servers with a multipath TCP listener. In the lab it leaked a kernel pointer in about 48 minutes and reached a shell five minutes later. The exploit is unpublished. Programs built with Go 1.24 or later open that kind of listener by default. These two commands show whether a host has one. Run them on the host itself, because a container uses the host's kernel.

$ ss -Mlnp                  # multipath TCP listeners
$ sysctl net.mptcp.enabled  # 1 means apps may open one

Debian, SUSE, Oracle and Amazon Linux ship fixed kernels, and a fix only takes effect after a reboot. Ubuntu and Red Hat Enterprise Linux are still waiting. Until they ship, drop incoming TCP packets that carry IPv4 options, which ordinary traffic almost never uses. This nftables rule does that. It narrows the exposure without fixing the kernel. If I ran Go services on Ubuntu, I would add this rule and turn off multipath TCP now, rather than wait for the kernel.

# drop IPv4 TCP packets that carry IP options
nft add table ip cve_2026_98432
nft add chain ip cve_2026_98432 pre '{ type filter hook prerouting priority -300; }'
nft add rule ip cve_2026_98432 pre meta l4proto tcp ip hdrlength gt 5 counter drop

Researchers at Parameter turned a public ChatGPT share into JavaScript running in the signed-in session of whoever opened it. It could list your chats, read a private one and send it off-site. The Preview sandbox held. But a graph had loaded a math library called MathLive, which accepted messages from any frame and rendered the HTML inside them. That HTML opened an unsandboxed frame, and a YouTube endpoint the page's security policy allowed ran the script. If your page listens for postMessage, check the sender, and never take raw HTML from it. OpenAI fixed it on October 26 and paid 5,000 dollars, which yellow_lead in the thread calls very low.

cfsolve is a Rust library and command line tool that hands back a Turnstile token, or the clearance cookie for a challenge page, with no browser running. It impersonates one recorded browser, Safari on iPhone, from a profile file. Its author, costco, wrote in the thread that it failed for one user on European proxies, and that Cloudflare constantly changes things. manofmanysmiles, who built something similar a year ago, says it worked until it didn't, because Cloudflare looks for patterns across its whole network.

$ challenge --page 'https://example.com/login' /tmp/solve \
    --solve --fingerprint profiles/safari-26-ios.json

Andrej Karpathy had Claude Opus 5.5 build HackerTube in about two hours. Opus pulled every Hacker News comment, ran Sonnet over them to cut spam, and kept about 40,000 that recommend a YouTube video. That comes to nearly 6,500 videos across 150 topics. There are no accounts, and your recommendations stay in your browser. The whole dataset downloads as a zip with a guide written for coding agents, so you can build your own version. reorder9695 finds its front page closer to what they want to watch than YouTube's personalised feed.