Prototype pollution in class-transformer

published 2020-04-06 6 y ago modified 2026-07-08 4 mo ago also GHSA-6gp3-h3jj-prx4 , EUVD-2020-0368

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.2%; EPSS 1.2% chance of exploitation in 30 days, percentile 68%
public exploits: 0; none known

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.

Patch / fix

fixed in 2 links 1

npm class-transformer 0.3.1
class-transformer_project class-transformer 0.3.1

github.com/typestack/class-transformer@8f04eb9 commit

Exploit prediction

1.19% chance of exploitation in the next 30 days, higher than 68% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

snyk.io https://snyk.io/vuln/SNYK-JS-CLASSTRANSFORMER-564431 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:P/A:N
GitHub	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	class-transformer	<0.3.1	0.3.1

Affected products

n/a class-transformer

Classification

Weakness

CWE-1321 Improperly Controlled Modification of Object Prototype Attributes
CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes

References

github.com /typestack/class-transformer/commit/8f04eb9db02de708f1a20f6f2d2bb309b2fed01e
web, patch, third-party-advisory
snyk.io /vuln/SNYK-JS-CLASSTRANSFORMER-564431
web, exploit, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2020-7637
advisory
github.com /typestack/class-transformer
package
github.com /typestack/class-transformer/blob/a650d9f490573443f62508bc063b857bcd5e2525/src/ClassTransformer.ts#L29-L31,
web

Sources

CVE List CVE-2020-7637
GitHub Advisory GHSA-6gp3-h3jj-prx4
NVD CVE-2020-7637

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary