CVE-2020-6820
Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run Firefox and Thunderbird, fix it now.
CISA required action: Apply updates per vendor instructions.
US federal civilian agencies must remediate by May 3, 2022.
Patch status
No official fix confirmed yet
Until a fix ships, follow the vendor's mitigations and CISA's required action, limit exposure of affected systems, and watch this record for a patch.
Description
Under certain conditions, when handling a ReadableStream, 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.
Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.
Affected products
| Product | Vendor | Affected versions | Fixed in | Source |
|---|---|---|---|---|
| Firefox | Mozilla | < 68.6.1; < 74.0.1; < 68.7.0 | 68.6.1; 74.0.1; 68.7.0 | NVD |
| Firefox and Thunderbird | Mozilla | — | — | KEV |
Sources: NVD = NIST National Vulnerability Database; KEV = CISA Known Exploited Vulnerabilities catalog.
Intelligence timeline
Developments from the last 30 days, newest first.
- CVSS scoredUpdateKEV
CVE-2020-6820 scored CVSS 8.1: Mozilla Firefox and Thunderbird, Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
CISA lists this as exploited in the wild. Unpatched Firefox and Thunderbird systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database
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Coverage
We have not published a story about this vulnerability yet.