CVE-2020-25739 json
Gon gem lack of escaping certain input when outputting as JSON
published 2020-09-23 6 y ago modified 2026-06-17 4 mo ago also GHSA-78vq-9j56-wrfr , EUVD-2021-0786
- cvss
- 6.1
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.4%
- EPSS 1.4% chance of exploitation in 30 days, percentile 72%
- public exploits
- 0
- none known
Summary
An issue was discovered in the gon gem before gon-6.4.0 for Ruby. MultiJson does not honor the escape_mode parameter to escape fields as an XSS protection mechanism. To mitigate, json_dumper.rb in gon now does escaping for XSS by default without relying on MultiJson.
Patch / fix
- rubygems gon 6.4.0
- gon_project gon 6.4.0
- ruby-gon Debian 12 6.4.0-1
debian advisories DEBIAN-CVE-2020-25739
- ruby-gon Ubuntu 18.04 LTS 6.1.0-1+deb9u1build0.18.04.1
ubuntu advisories UBUNTU-CVE-2020-25739
Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0
- github.com/gazay/gon@fe3c7b2 commit
Exploit prediction
1.38% chance of exploitation in the next 30 days, higher than 72% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| NVD | 2.0 | 4.3 | AV:N/AC:M/Au:N/C:N/I:P/A:N |
| GitHub | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| rubygems | gon | <6.4.0 |
6.4.0 |
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
github.com
/gazay/gon/commit/fe3c7b2191a992386dc9edd37de5447a4e809bc7
web, patch, third-party-advisory
-
usn.ubuntu.com
/4560-1/
vendor-advisory, third-party-advisory
-
lists.debian.org
/debian-lts-announce/2020/09/msg00018.html
mailing-list, web, third-party-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2020-25739
advisory
-
github.com
/gazay/gon
package
-
github.com
/rubysec/ruby-advisory-db/blob/master/gems/gon/CVE-2020-25739.yml
web
-
usn.ubuntu.com
/4560-1
web
Sources
- CVE List CVE-2020-25739
- GitHub Advisory GHSA-78vq-9j56-wrfr
- NVD CVE-2020-25739
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.