CVE-2020-6820 Mozilla Firefox and Thunderbird: memory-safety flaw
In plain words: The program mishandles the memory it uses to keep track of data. A specially made input can scramble that memory. Usually lets an attacker crash the program or run their own code with its permissions.
Confirmed exploited by CISA on · US federal patch deadline May 3, 2022
What to do
- Install Mozilla's security update for Firefox and Thunderbird. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Let the browser auto-update and relaunch it when it asks — the fix is not active until you do.
- Keep extensions to a minimum and remove ones you do not recognise.
- Stop using Internet Explorer and any browser that no longer gets updates.
Who is affected
Could reach you. This one is aimed at devices or apps of the kind people own.
What's at risk: A malicious or hacked website can be enough. Browser bugs are often the first step in a longer attack on the whole computer or phone.
The details
- Official name
- Mozilla Firefox And Thunderbird Use-After-Free Vulnerability
- Product
- Mozilla Firefox and Thunderbird
- CISA description
- Mozilla Firefox and Thunderbird contain a race condition vulnerability when handling a ReadableStream under certain conditions. The race condition creates a use-after-free vulnerability, causing unspecified impacts.
- Type of flaw
- Memory-safety flaw (CWE-362)
- Confirmed exploited
- Nov 3, 2021
- US federal patch deadline
- May 3, 2022
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Questions about CVE-2020-6820
Is CVE-2020-6820 being exploited?
Yes. CISA added CVE-2020-6820 to its Known Exploited Vulnerabilities catalog on Nov 3, 2021, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2020-6820?
Install Mozilla's security update for Firefox and Thunderbird. If no update exists, follow the vendor's workaround or stop using the product until one ships. Let the browser auto-update and relaunch it when it asks — the fix is not active until you do.
Am I affected by CVE-2020-6820?
Only if you use Mozilla Firefox and Thunderbird. This one is aimed at devices or apps of the kind people own.