Rollbar.js Prototype Pollution Vulnerability in merge()

published 2025-10-23 12 mo ago modified 2026-10-08 32 d ago also GHSA-xcg2-9pp4-j82x , EUVD-2025-35708

cvss: 5.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits: 0; none known

Rollbar.js offers error tracking and logging from Javascript to Rollbar. In versions before 2.26.5 and from 3.0.0-alpha1 to before 3.0.0-beta5, there is a prototype pollution vulnerability in merge(). If application code calls rollbar.configure() with untrusted input, prototype pollution is possible. This issue has been fixed in versions 2.26.5 and 3.0.0-beta5. A workaround involves ensuring that values passed to rollbar.configure() do not contain untrusted input.

Patch / fix

fixed in 1 links 4

npm rollbar 2.26.5, 3.0.0-beta5

github.com/rollbar/rollbar.js@61032fe commit
github.com/rollbar/rollbar.js@d717def commit
github.com/rollbar/rollbar.js#1390 pull request
github.com/rollbar/rollbar.js#1394 pull request

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 12 mo ago (2025-10-23)

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
GitHub	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	rollbar	<2.26.5 >=3.0.0-alpha1, <3.0.0-beta5	2.26.5 3.0.0-beta5

Affected products

rollbar rollbar.js

Classification

Weakness

CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

Sources

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