CVE-2020-6806
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.61%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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.
- CVSS 3.1
- 8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- EPSS
- 2.61% probability · 85th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-125
- Affected
- mozilla/firefox · mozilla/firefox esr · mozilla/thunderbird · canonical/ubuntu linux
- Source
- security@mozilla.org
EPSS 2.6% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://packetstormsecurity.com/files/157524/Firefox-js-ReadableStreamCloseInternal-Out-Of-Bounds-Access.htmlThird Party Advisory, VDB Entry
- https://bugzilla.mozilla.org/show_bug.cgi?id=1612308Issue Tracking, Permissions Required
- https://usn.ubuntu.com/4328-1/Third Party Advisory
- https://usn.ubuntu.com/4335-1/Third Party Advisory
- https://www.mozilla.org/security/advisories/mfsa2020-08/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2020-09/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2020-10/Vendor Advisory
- http://packetstormsecurity.com/files/157524/Firefox-js-ReadableStreamCloseInternal-Out-Of-Bounds-Access.htmlThird Party Advisory, VDB Entry
- https://bugzilla.mozilla.org/show_bug.cgi?id=1612308Issue Tracking, Permissions Required
- https://usn.ubuntu.com/4328-1/Third Party Advisory
- https://usn.ubuntu.com/4335-1/Third Party Advisory
- https://www.mozilla.org/security/advisories/mfsa2020-08/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2020-09/Vendor Advisory
- https://www.mozilla.org/security/advisories/mfsa2020-10/Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.