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CVE-2020-15866

30
FAUCET Score

CVE-2020-15866 is a critical heap-based buffer overflow vulnerability affecting mruby versions through 2.1.2-rc, specifically within the mrb_yield_with_class function due to incorrect VM stack handling. This flaw can be triggered remotely without authentication, leading to complete compromise of confidentiality, integrity, and availability. While no public exploits or active exploitation have been confirmed, the vulnerability has garnered significant community discussion, indicating potential interest.

Impacted Technologies

VendorProductVersion(s)CPE
<= 2.1.1CPE matchmatch criteria
cpe:2.3:a:mruby:mruby:*:*:*:*:*:*:*:*
2.1.2CPE matchmatch criteria
cpe:2.3:a:mruby:mruby:2.1.2:rc:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.09%
Probability of exploitation in next 30 days
EPSS Percentile
79.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0209 is in the 69th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / mruby/mruby/issues/5042
ExploitThird Party Advisory
lists.debian.org / debian-lts-announce/2022/05/msg00006.html
Mailing ListThird Party Advisory