SARA / Free Tools / CVE / CVE-2020-6819

CVE-2020-6819 — Mozilla Firefox And Thunderbird Use-After-Free Vulnerability

Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.

CVSS
EPSS
36.00% (top 42.00%)
CWE
Published
2020-04-24T15:56:56.000Z
Last modified
2025-10-21T23:35:45.566Z
CVSS vector
CISA KEV — Actively Exploited
Added to KEV
2021-11-03
BOD 22-01 due
2022-05-03
Ransomware use
Unknown

01What is this vulnerability?

Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.

02Affected products

VendorProductVersions
MozillaThunderbirdunspecified
MozillaFirefoxunspecified
MozillaFirefox ESRunspecified

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2021-11-03. Ransomware use: Unknown.

04Recommended remediation

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

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07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

09References

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