CVE-2020-6806

8.8 highEPSS 2.6%

High (8.8). EPSS 2.6% chance of exploitation in the next 30 days.

By carefully crafting promise resolutions, it was possible to cause an out-of-bounds read off the end of an array resized during script execution. This could have led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 68.6, Firefox < 74, Firefox < ESR68.6, and Firefox ESR < 68.6.

Severity

CVSS 3.1

8.8 high

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS: 2.6% chance of exploitation in the next 30 days; higher than 85% of CVEs (scores of 2026-10-31)
CWE: CWE-125
Published: 2020-03-25
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Affected

canonical:ubuntu_linux
mozilla:firefox
mozilla:firefox_esr
mozilla:thunderbird

References

http://packetstormsecurity.com/files/157524/Firefox-js-ReadableStreamCloseInternal-Out-Of-Bounds-Access.html
https://bugzilla.mozilla.org/show_bug.cgi?id=1612308
https://usn.ubuntu.com/4328-1/
https://usn.ubuntu.com/4335-1/
https://www.mozilla.org/security/advisories/mfsa2020-08/

Check your stack JSON