Trezor Hack Scare: That STM32 Entropy Email Is a Phishing Attack

If a message titled "Critical Security Alert: STM32 Entropy Vulnerability" landed in your inbox this week, apparently from Trezor, telling you that one in four devices shipped with a defective chip and inviting you to run an entropy check in your browser, stop. Do not click anything in it. Trezor did not send it.

The company confirmed on Wednesday that attackers had gotten into its email infrastructure and used it to blast a fake security warning to customers. The email is a seed harvester dressed up as an apology, and it is one of the more convincing phishing attempts the hardware wallet space has seen in years.

What Does the Fake Trezor Security Alert Actually Claim?

The email opens with the tone of a company confessing to a disaster. It claims Trezor's engineering team found a hardware-level defect in the STM32 microcontrollers inside its devices, that the flaw was baked in at the factory, and that roughly one device in four is affected. It says the bug produces recovery phrases with as little as 40 bits of entropy, leaving seeds open to brute-force cracking.

It then does something clever. It tells the reader never to enter a recovery phrase on a website or share it with anyone. Two paragraphs later, it invites that same reader to click a link and run an "entropy check tool" that verifies BIP-39 checksums across 12, 18 and 24-word phrases, validates SLIP-39 shares, and exports extended public keys.

That contradiction is the entire scam. The warning buys credibility, then the tool collects exactly what the warning told you to protect. Anyone who works through that checker hands over enough material to drain their wallet, and in the case of an xpub export, hands over a full map of their addresses and balances even without the seed.

Why Did Trezor Users Fall For The STM32 Story?

Because a nearly identical bug was real six weeks ago, just at a different company.

Starting on 30 July 2026, attackers exploited a firmware flaw in Coinkite's Coldcard wallets. A regression shipped in March 2021 caused affected devices to generate seed phrases using a weak software randomness source instead of the hardware random number generator, cutting effective entropy from around 128 bits to as low as 40 bits on some models. Attackers drained roughly 1,816 BTC, close to 116 million dollars, from more than 5,200 addresses across four waves. Later tallies pushed the figure past 130 million dollars.

Read that against the phishing email again. Forty bits of entropy. Seeds generated before a cutoff date. Brute-force exposure. Migrate to a new seed. The scammers did not invent a threat model. They copied a documented one, swapped the brand name, and sent it to a customer list that had spent August reading about exactly this failure mode. That is why it worked on people who normally spot phishing at a glance.

How Did The Phishing Email Come From A Real Trezor Address?

This is the part that stripped away the usual defences. The message did not arrive from a lookalike domain with a swapped character. It arrived through Trezor's own legitimate sending infrastructure after attackers compromised a third-party email provider.

Trezor said it took down the domain used in the attack and is investigating how the attackers gained access to its legitimate domain. The company has said wallets, private keys and recovery backups stored on devices were never exposed. The compromise sat in the marketing pipeline, not the product.

The problem may be wider than one brand. Casa co-founder Nick Neuman said he had heard of the same campaign hitting Bitbox users and suggested a shared marketing email provider had been compromised.

What Should Trezor Owners Do Right Now?

If you only opened and read the email, nothing has happened to your funds. Delete it and move on.

If you clicked the link and entered any portion of your recovery phrase, a SLIP-39 share, or your device PIN into that page, treat the seed as burned. Generate a fresh seed on a device you trust and move everything to the new addresses immediately. Do not wait to see whether anything happens, and do not reuse the old backup for anything.

If you exported an extended public key, your funds are not directly at risk, but the attacker can now watch your balances and link your addresses. That makes you a target for follow-up scams, including phone calls and physical letters, both of which Trezor customers have already reported this year.

Going forward, the rule is unchanged and it is the only rule that matters. No legitimate wallet manufacturer will ever ask you to type your recovery phrase into a browser, for any reason, including a check that claims to protect you. Verify announcements on trezor.io or the verified Trezor account on X, and treat unexpected email as hostile regardless of what address it appears to come from.

Is This Part Of A Bigger Pattern In 2026?

It is, and the pattern is not about broken devices.

This is the third failure at a Trezor vendor in four weeks. An August incident at ShipMonk, the partner handling Trezor order fulfilment, pushed the number of exposed customers above 80,000 by early September, leaking names, phone numbers and home addresses. Trezor had already warned 66,000 users after a support portal breach in 2024, and rival SafePal leaked close to 40,000 records last month.

The hardware keeps holding. The companies sitting around the hardware, holding customer contact details, keep leaking. Combine a leaked customer list with a compromised sending domain and a real vulnerability at a competitor, and you get a phishing email that reads like the genuine article.

For anyone holding coins on a hardware wallet, the practical takeaway is that your device being secure and your data being secure are now two separate questions, and only one of them is in your hands.