CVE-2018-4939
CVE-2018-4939 is a security flaw in Adobe ColdFusion, Adobe’s platform for building web applications. Attackers can run their own code on Adobe ColdFusion. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021.[1]
Adobe ColdFusion 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. Adobe has published a fix or advice.
Description
CISA calls it a deserialization of untrusted data in Adobe ColdFusion. In its words: “Adobe ColdFusion contains a deserialization of untrusted data vulnerability that could allow for code execution.”[1]
The CVE record adds: “Adobe ColdFusion Update 5 and earlier versions, ColdFusion 11 Update 13 and earlier versions have an exploitable Deserialization of Untrusted Data vulnerability. Successful exploitation could lead to arbitrary code execution.”[2]
The underlying weakness is deserialization of untrusted data (CWE-502), in MITRE’s list of common software weaknesses.
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; Adobe’s advisory has them[3]. CISA names the product as Adobe ColdFusion.
Most families won’t have Adobe ColdFusion; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 1,264 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 3 May 2022 to fix it.[1]
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 62%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Adobe has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Adobe ColdFusion 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.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 3 May 2022 to fix it.
- 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
| Date | Event |
|---|---|
| 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.[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 62%.[4] |
See also
Other Adobe ColdFusion flaws
- CVE-2026-48282: path traversal ·
- CVE-2017-3066: deserialization ·
- CVE-2024-20767: improper access control ·
- CVE-2023-38203: deserialization of untrusted data ·
- CVE-2023-29300: deserialization of untrusted data ·
- CVE-2023-26359: deserialization of untrusted data ·
Other Adobe flaws
- CVE-2026-48356, Adobe Commerce and Magento: unrestricted upload of file with dangerous type ·
- CVE-2026-71362, Adobe Commerce and Magento: incorrect authorization ·
- CVE-2026-75650, Adobe Commerce and Magento: improper neutralization of special elements used in a template engine ·
- CVE-2009-3459, Adobe Acrobat and Reader: heap-based buffer overflow ·
- CVE-2026-34621, Adobe Acrobat and Reader: prototype pollution ·
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-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
Every Adobe flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “Adobe ColdFusion Deserialization of Untrusted Data Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2018-4939 Detail”. National Vulnerability Database, published 19 May 2018.
- ^ Adobe. Advisories and fixes: helpx.adobe.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.618, percentile 99.2, 31 Oct 2026.
- CVE Program. “CVE-2018-4939”. 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.