PatchTheCVECVE-2020-7637: class-transformer before 0.3.1 allow attackers to perform Prototype Pollution
CVE-2020-7637 is a medium-severity flaw (CVSS 5.3) affecting class-transformer. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
class-transformer before 0.3.1 allow attackers to perform Prototype Pollution. The classToPlainFromExist function could be tricked into adding or modifying properties of Object.prototype using a __proto__ payload.
Why this priority
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.2% (top 32%) |
| CISA exploited list | No |
| Weakness | CWE-1321 |
| Published | 2020-04-06 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2020-7637?
class-transformer: upgrade to 0.3.1. Exact commands for each OS are on this page.
Is CVE-2020-7637 being exploited?
CVE-2020-7637 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2020-7637 affect?
CVE-2020-7637 affects class-transformer. Severity is medium (CVSS 5.3). class-transformer before 0.3.1 allow attackers to perform Prototype Pollution. The classToPlainFromExist function could be tricked into adding or modifying properties of Object.prototype using a __proto__ payload.
How urgent is CVE-2020-7637?
Priority 46/100. Public exploit reference; Remotely exploitable, no login, no user action