When multiple WASM threads had a reference to a module, and were looking up exported functions, one WASM thread could have overwritten anot…

published 2020-10-22 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-7668

cvss: 7.5; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.1%; EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits: 0; none known

When multiple WASM threads had a reference to a module, and were looking up exported functions, one WASM thread could have overwritten another's entry in a shared stub table, resulting in a potentially exploitable crash. This vulnerability affects Firefox < 82.

Patch / fix

fixed in 1 distros 4

Mozilla Firefox 82

ubuntu opensuse alpine arch linux

firefox Ubuntu 16.04 LTS 82.0+build2-0ubuntu0.16.04.5
firefox Ubuntu 18.04 LTS 82.0+build2-0ubuntu0.18.04.1
firefox Ubuntu 20.04 LTS 82.0+build2-0ubuntu0.20.04.1

ubuntu advisories UBUNTU-CVE-2020-15681

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

firefox-esr openSUSE Tumbleweed 128.5.1-1.1
MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 82.0-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 82.0-r0

alpine advisories ALPINE-CVE-2020-15681

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

firefox Arch Linux 82.0-1

arch linux advisories AVG-1256

Exploit prediction

1.09% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

Mozilla Firefox

References

mozilla.org /security/advisories/mfsa2020-45/
release-notes, vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1666568
issue-tracking, permissions-required, vendor-advisory

Sources

CVE List CVE-2020-15681
NVD CVE-2020-15681

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary