CVE-2020-6838Public exploit

Freed-memory read via reallocated VM argument stack

Published Jan 11, 2020 · Updated Aug 4, 2024

Use-after-free in mruby 2.1.0 Hash#values_at allows attackers to read freed heap memory via crafted hash keys and arguments. The function retains an argument pointer into the VM stack while hash-key equality calls can extend and reallocate that stack, then dereferences the stale pointer. Triggering the flaw requires execution of crafted Ruby code; the published proof of concept demonstrates an AddressSanitizer-detected heap read and process abort, not code execution.

CVSS severity9.8
Critical
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Use-after-free in mruby 2.1.0 Hash#values_at allows attackers to read freed heap memory via crafted hash keys and arguments. The function retains an argument pointer into the VM stack while hash-key equality calls can extend and reallocate that stack, then dereferences the stale pointer. Triggering the flaw requires execution of crafted Ruby code; the published proof of concept demonstrates an AddressSanitizer-detected heap read and process abort, not code execution.

The record

CVE
CVE-2020-6838
Published
Jan 11, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Jan 11, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo