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CVE-2018-1000539

18
FAUCET Score

CVE-2018-1000539 is a medium-severity vulnerability affecting json-jwt versions 0.5.0 through 1.9.3, allowing an attacker to forge authentication tags in AES-GCM encrypted JSON Web Tokens due to improper cryptographic signature verification (CWE-347). This network-exploitable flaw could lead to unauthorized data modification (low integrity impact) without requiring user interaction or elevated privileges. While the vulnerability has a CVSS score of 5.3, there is no evidence of active exploitation, public exploit code, or significant community discussion, and it is not listed in the KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.5.0, < 1.9.4CPE matchmatch criteria
cpe:2.3:a:json-jwt_project:json-jwt:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

5.3MEDIUM

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.0

Exploit Intelligence

EPSS Score
0.78%
Probability of exploitation in next 30 days
EPSS Percentile
52.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0078 is in the 33rd percentile among its peer group of 23,723 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

rubygemspatch availablevia ghsa
Product: json-jwtFixed in: 1.9.4

Vendor Advisories (1)

rubygemsGHSA-mj4x-wcxf-hm8xmedium

Json-jwt did not verify the cryptographic signature for data

Jul 31, 2018

References

github.com / nov/json-jwt/pull/62
Third Party Advisory
debian.org / security/2018/dsa-4283