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CVE-2023-43208

From Exploited flaws, HARD’s guide to the flaws being used in attacks · Checked
This article is about a flaw in NextGen Healthcare Mirth Connect. For every flaw being used in attacks, see Exploited flaws.

CVE-2023-43208 is a security flaw in NextGen Healthcare Mirth Connect. Attackers can run their own code on NextGen Healthcare Mirth Connect from anywhere, without logging in. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 20 May 2024, and says ransomware gangs have used it.[1]

NextGen Healthcare Mirth Connect is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff.

Description

CISA calls it a deserialization of untrusted data in NextGen Healthcare Mirth Connect. In its words: “NextGen Healthcare Mirth Connect contains a deserialization of untrusted data vulnerability that allows for unauthenticated remote code execution via a specially crafted request.”[1]

The underlying weakness is deserialization of untrusted data (CWE-502), in MITRE’s list of common software weaknesses.[2]

It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]

Affected versions

NVD’s record doesn’t list version ranges for it. CISA names the product as NextGen Healthcare Mirth Connect.

Most families won’t have NextGen Healthcare Mirth Connect; it’s for whoever looks after IT at work.

Exploitation

CISA added it to its catalog of known exploited vulnerabilities on 20 May 2024, 207 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 10 Jun 2024 to fix it.[1] CISA says ransomware gangs have used it.

FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 86%. That’s in the top 1% of the flaws it scores.[3]

CISA assesses it as automatable: attackers can run it against many targets at once.

CISA doesn’t say who was attacked, or how.

Fix

CISA’s required action: “Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.”[1]

  1. Check whether you use it.NextGen Healthcare Mirth Connect is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
  2. Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 10 Jun 2024 to fix it.
  3. If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.

You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.

Timeline

DateEvent
The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2]
CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1]
CISA’s deadline for US government agencies to fix it.[1]
FIRST puts the odds of it being used in attacks in the next 30 days at 86%.[3]

See also

Other deserialization of untrusted data flaws

  • CVE-2021-23758, Ajax.NET Professional: deserialization of untrusted data ·
  • CVE-2026-63077, JetBrains TeamCity: deserialization of untrusted data ·
  • CVE-2026-50522, Microsoft SharePoint: deserialization of untrusted data ·
  • CVE-2026-58644, Microsoft SharePoint: deserialization of untrusted data ·
  • CVE-2026-45659, Microsoft SharePoint Server: deserialization of untrusted data ·

Added the same day

  • CVE-2024-4947, Chrome and other Chromium browsers: type confusion ·

References

  1. ^ Cybersecurity and Infrastructure Security Agency. “NextGen Healthcare Mirth Connect Deserialization of Untrusted Data Vulnerability”. Known Exploited Vulnerabilities Catalog, added 20 May 2024.
  2. ^ National Institute of Standards and Technology. “CVE-2023-43208 Detail”. National Vulnerability Database, published 26 Oct 2023.
  3. ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.859, percentile 99.7, 31 Oct 2026.
  4. CVE Program. “CVE-2023-43208”. The official CVE record.

This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.