CVE-2020-36208Public exploit

Memory corruption via missing OnceCell Send bound

Published Jan 22, 2021 · Updated Aug 4, 2024

Memory corruption in the conquer-once crate before 0.3.2 allows local users to trigger undefined behavior in concurrent programs. OnceCell's unsafe Sync implementation accepts T: Sync without also requiring T: Send, allowing a non-Send value such as MutexGuard to cross thread boundaries. Exploitation requires local code that places a non-Send but Sync value in an affected OnceCell; handling that value on another thread can corrupt memory.

CVSS severity7.8
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in the conquer-once crate before 0.3.2 allows local users to trigger undefined behavior in concurrent programs. OnceCell's unsafe Sync implementation accepts T: Sync without also requiring T: Send, allowing a non-Send value such as MutexGuard to cross thread boundaries. Exploitation requires local code that places a non-Send but Sync value in an affected OnceCell; handling that value on another thread can corrupt memory.

The record

CVE
CVE-2020-36208
Published
Jan 22, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-662, CWE-787
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Jan 22, 2021CVE 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

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8GitHub Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:L/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.

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No observations available

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

Weakness, pattern, technique

CWE-662Improper Synchronization
CWE-787Out-of-bounds Write

Public exploit references

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

Technologies

Your stack

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Your stack

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