Two critical Firefox vulnerabilities exploited by attackers, patch now!
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2020-6820 +1 in the same advisory: …6819 | Use-after-free (race condition) in Mozilla Firefox and Thunderbird CVE-2020-6820 is a use-after-free vulnerability in Mozilla's Gecko-based products caused by a race condition (CWE-362) that occurs under certain conditions when handling a ReadableStream. It is triggered by attacker-controlled content, such as a crafted web page or email content processed by Thunderbird, that drives the timing race; the high attack complexity (AC:H in the CVSS vector) reflects the need to hit the right timing window. Successful exploitation corrupts freed memory and can compromise confidentiality, integrity, and availability (all rated high in the CVSS 8.1 score), typically enabling code execution within the affected application. All users of Firefox < 74.0.1, Firefox ESR < 68.6.1, and Thunderbird < 68.7.0 are affected — effectively the entire unpatched Firefox and Thunderbird installed base at the time of the emergency release. Mozilla confirmed targeted attacks in the wild abusing this flaw at disclosure, it was added to CISA's Known Exploited Vulnerabilities catalog on 2021-11-03, and EPSS currently assigns a 7.1% 30-day exploitation probability (94th percentile). Do: Upgrade Firefox to 74.0.1 or later, Firefox ESR to 68.6.1 or later, and Thunderbird to 68.7.0 or later, per the vendor advisories and CISA KEV required action. No workaround is documented, so inventory client fleets for versions below these releases and prioritize patching, especially for users who browse untrusted sites or open untrusted mail; disabling JavaScript can serve only as a temporary stopgap. | 8.1 | 7% | KEV |
| masshundreds of millions of users (Firefox's global monthly user base, plus tens of millions of Thunderbird installs) |
Full article247 words · extracted from helpnetsecurity.com · click to collapse
Mozilla has released critical security updates for Firefox and Firefox ESR on Friday, patching two vulnerabilities that are being actively exploited by attackers.
fixed in Firefox 74.0.1 and Firefox ESR 68.6.1 are:
- CVE-2020-6819: A use-after-free flaw caused by a race condition while running the nsDocShell destructor
- CVE-2020-6820: A use-after-free caused by a race condition when handling a ReadableStream
No additional details about them have been provided and the bug entries in Mozilla’s bug database are still unaccessible to the wider public. The bugs have been rated “critical”, which means that chances are high they can lead to remote code execution (whether individually or concatenated together).
The vulnerabilities (and presumably their active exploitation) have been flagged by security researchers Francisco Alonso and Javier Marcos.
One of Alonso’s comments on Twitter seems to indicate that the flaws may also affect other browsers:
There is still lots of work to do and more details to be published (including other browsers). Stay tuned.
— Francisco Alonso (@revskills) April 3, 2020
Update ASAP
Home users and enterprise admins are advised to implement the provided updates as soon as possible.
I would also urge home users to think about making Firefox update itself every time a new update is made available, as recommended by Mozilla. If you generally don’t think twice about installing offered updates, the “Automatically install updates” option might be the right thing for you.
The last actively exploited Firefox zero-day vulnerability before these was patched in January 2020.
Text extracted automatically; images, tables and formatting may be missing. Original: https://www.helpnetsecurity.com/2020/04/06/firefox-vulnerabilities-exploited/