Johnson & Johnson is telling patients that it has learned of a cyber security bug in one of its insulin pumps that a hacker could exploit to overdose diabetic patients with insulin, though it describes the hacking risk as low.

Medical device experts said they believe it was the first time a manufacturer had issued such a warning to patients about a cyber vulnerability, a hot topic in the industry following revelations last month about possible vulnerabilities in pacemakers and defibrillators.

J&J jnj executives told Reuters they knew of no examples of attempted attacks on the device, the J&J Animas OneTouch Ping insulin pump. The company is nonetheless warning customers and providing advice on how to fix the problem.

“The probability of unauthorized access to the OneTouch Ping system is extremely low,” the company said in letters mailed out on Monday to doctors and about 114,000 patients in the United States and Canada who use the device. A copy of the text of the letter was made available to Reuters.

The warning is being delivered a month after a prominent short seller and cyber security research firm went public with allegations of potentially life-threatening cyber vulnerabilities in heart devices from St. Jude Medical Inc .

St. Jude said the allegations were false as its shares tumbled and the U.S. Food and Drug Administration began an investigation.

The U.S. Food and Drug Administration is preparing to release formal guidance on how medical device makers should handle reports about cyber vulnerabilities. J&J said it reviewed the matter with the FDA before sending the letter.

An early draft of that guidance, which was released in January for public comments, calls for device makers to work with security researchers, identify steps to mitigate risks, and provide patients with information about bugs so they can “make informed decisions” about device use.

The FDA declined comment on J&J’s handling of the vulnerability in the insulin pump, a medical device that patients attach to their bodies that injects insulin through catheters.

J&J executives told Reuters that they worked on the security problems with Jay Radcliffe, a diabetic and well-known medical-device hacking researcher with cyber security firm Rapid7 who reported vulnerabilities in the pump to the company in April.

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The Animas OneTouch Ping is sold with a wireless remote control that patients can use to order the pump to dose insulin so that they do not need access to the device itself, which is typically worn under clothing and could be awkward to reach.

Radcliffe said he identified ways for a hacker to spoof communications between the remote control and the OneTouch Ping insulin pump, potentially forcing it to deliver unauthorized insulin injections. Dosing a patient with too much insulin could cause hypoglycemia, or low blood sugar, which in extreme cases can be life threatening, said Brian Levy, chief medical officer with J&J’s diabetes unit.

The system is vulnerable because those communications are not encrypted, or scrambled, to prevent hackers from gaining access to the device, Radcliffe said.

Company technicians were able to replicate Radcliffe’s findings, confirming that a hacker could order the pump to dose insulin from a distance of up to 25 feet, Levy said. He said such attacks are difficult to pull off because they require specialized technical expertise and sophisticated equipment.

“We believe the OneTouch Ping system is safe and reliable. We urge patients to stay on the product,” Levy said.

J&J’s letter said that if patients were concerned, they could take several steps to thwart potential attacks. They include discontinuing use of a wireless remote control and programming the pump to limit the maximum insulin dose.

Radcliffe said he believed that OneTouch Ping users would be safe if they followed the steps outlined in the letter from J&J.

“They can give peace of mind to the patient or parent of a child using the device,” he said.

J&J Chief Information Security Officer Marene Allison said her team would make sure other J&J products do not have similar bugs.

Radcliffe said he found vulnerabilities in the Animas OneTouch Ping, but not the Animas Vibe line of insulin pumps.

Suzanne Schwartz, an FDA official responsible for reviewing bugs in medical devices, said in a statement that she encourages collaboration between researchers and device manufacturers to identify, remediate and alert the public to vulnerabilities.

“It enables all stakeholders to better address device safety with the interest of patient health in mind,” she said.

The FDA has said it knows of no cases where hackers have exploited cyber vulnerabilities to harm a patient.

The agency last year issued multiple warnings about cyber bugs in infusion pumps from Hospira, which has since been acquired by Pfizer Inc.