Read the docs
TI-2020-05529 Aliases CVE-2020-6820GHSA-f77r-rqc9-53hh

Race condition in Mozilla Thunderbird

Priority CRITICAL 94Exploited in the wildCWE-362Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 15 fixed, 1 without a fix

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and Red Hat.

Summary

Under certain conditions, when handling a ReadableStream, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Thunderbird < 68.7.0, Firefox < 74.0.1, and Firefox ESR < 68.6.1.

Why it matters now

Exploitation Active In CISA KEV since 2021-11-03CISA due date 2022-05-03
EPSS 0.07063 94th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 68.7.0Firefox (Mozilla): 74.0.1+1 more productRed Hat: 8 advisoriesRed Hat: 15 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Active
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaThunderbirdbefore 68.7.068.7.0Patch availableCNA
MozillaFirefoxbefore 74.0.174.0.1Patch availableCNA
MozillaFirefox ESRbefore 68.6.168.6.1Patch availableCNA
  • Thunderbird VendorMozilla Affected before 68.7.0 Fixed in 68.7.0 Patch available CNA
  • Firefox VendorMozilla Affected before 74.0.1 Fixed in 74.0.1 Patch available CNA
  • Firefox ESR VendorMozilla Affected before 68.6.1 Fixed in 68.6.1 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*before 68.6.1VulnerableMozilla
cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*before 74.0.1VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 68.7.0VulnerableMozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* Versions before 68.6.1 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* Versions before 74.0.1 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 68.7.0 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Thunderbird (Mozilla) Fixed in 68.7.0
  • Fix · CNA Firefox (Mozilla) Fixed in 74.0.1
  • Fix · CNA Firefox ESR (Mozilla) Fixed in 68.6.1

Red Hat 8 advisories

  • RHSA-2020:1495 Released 2020-04-16 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-68.7.0-1.el8_1
  • RHSA-2020:1496 Released 2020-04-16 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird-68.7.0-1.el8_0
  • RHSA-2020:1488 Released 2020-04-16 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Desktop (v. 6) thunderbird-68.7.0-1.el6_10
    • Red Hat Enterprise Linux Server Optional (v. 6) thunderbird-68.7.0-1.el6_10
    • Red Hat Enterprise Linux Workstation (v. 6) thunderbird-68.7.0-1.el6_10
Show 5 more Red Hat advisories
  • RHSA-2020:1489 Released 2020-04-16 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-68.7.0-1.el7_8
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-68.7.0-1.el7_8
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-68.7.0-1.el7_8
  • RHSA-2020:1338 Released 2020-04-07 · Red Hat rating Critical
    firefox security update
    • Red Hat Enterprise Linux Client (v. 7) firefox-68.6.1-1.el7_8
    • Red Hat Enterprise Linux Client Optional (v. 7) firefox-68.6.1-1.el7_8
    • Red Hat Enterprise Linux Server (v. 7) firefox-68.6.1-1.el7_8
    • Red Hat Enterprise Linux Server Optional (v. 7) firefox-68.6.1-1.el7_8
    • Red Hat Enterprise Linux Workstation (v. 7) firefox-68.6.1-1.el7_8
    • Red Hat Enterprise Linux Workstation Optional (v. 7) firefox-68.6.1-1.el7_8
  • RHSA-2020:1339 Released 2020-04-07 · Red Hat rating Critical
    firefox security update
    • Red Hat Enterprise Linux Desktop (v. 6) firefox-68.6.1-1.el6_10
    • Red Hat Enterprise Linux Desktop Optional (v. 6) firefox-68.6.1-1.el6_10
    • Red Hat Enterprise Linux HPC Node Optional (v. 6) firefox-68.6.1-1.el6_10
    • Red Hat Enterprise Linux Server (v. 6) firefox-68.6.1-1.el6_10
    • Red Hat Enterprise Linux Server Optional (v. 6) firefox-68.6.1-1.el6_10
    • Red Hat Enterprise Linux Workstation (v. 6) firefox-68.6.1-1.el6_10
    • Red Hat Enterprise Linux Workstation Optional (v. 6) firefox-68.6.1-1.el6_10
  • RHSA-2020:1341 Released 2020-04-07 · Red Hat rating Critical
    firefox security update
    • Red Hat Enterprise Linux AppStream (v. 8) firefox-68.6.1-1.el8_1
  • RHSA-2020:1340 Released 2020-04-07 · Red Hat rating Critical
    firefox security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.0) firefox-68.6.1-1.el8_0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Mozilla Thunderbird 68.7.0

    5 records Highest priority Priority CRITICAL 2 CRITICAL, 2 MEDIUM, 1 LOW

    Other records, highest priority first

    • TI-2020-05528 Use after free in Mozilla ThunderbirdPriority CRITICAL 94
    • TI-2020-05534 Out-of-bounds write in Mozilla ThunderbirdPriority MEDIUM 46
    • TI-2020-05531 Out-of-bounds write in Mozilla ThunderbirdPriority MEDIUM 41
    Show all 5 records →
  • Release ·

    Mozilla Firefox, Firefox ESR 68.6.1, 74.0.1

    2 records Highest priority Priority CRITICAL 2 CRITICAL

    Other records, highest priority first

    • TI-2020-05528 Use after free in Mozilla ThunderbirdPriority CRITICAL 94
    Show all 2 records →

Vendor assessments

Red Hat

Red Hat rating: Critical. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 5AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2020:1341, RHSA-2020:1495
Red Hat Enterprise Linux AppStream E4S (v. 8.0)Fixed RHSA-2020:1340, RHSA-2020:1496
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2020:1338, RHSA-2020:1489
Red Hat Enterprise Linux Client Optional (v. 7)Fixed RHSA-2020:1338
Red Hat Enterprise Linux Desktop (v. 6)Fixed RHSA-2020:1339, RHSA-2020:1488
Red Hat Enterprise Linux Desktop Optional (v. 6)Fixed RHSA-2020:1339
Red Hat Enterprise Linux HPC Node Optional (v. 6)Fixed RHSA-2020:1339
Red Hat Enterprise Linux Server (v. 6)Fixed RHSA-2020:1339
Red Hat Enterprise Linux Server (v. 7)Fixed RHSA-2020:1338
Red Hat Enterprise Linux Server Optional (v. 6)Fixed RHSA-2020:1339, RHSA-2020:1488
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2020:1338, RHSA-2020:1489
Red Hat Enterprise Linux Workstation (v. 6)Fixed RHSA-2020:1339, RHSA-2020:1488
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2020:1338, RHSA-2020:1489
Red Hat Enterprise Linux Workstation Optional (v. 6)Fixed RHSA-2020:1339
Red Hat Enterprise Linux Workstation Optional (v. 7)Fixed RHSA-2020:1338

Timeline

  1. 2021-11-03 Added to CISA KEV
  2. 2026-10-02 Threatist record created from CVE-2020-6820
  3. 2026-10-03 Alias added: GHSA-f77r-rqc9-53hh

References

Advisory 3

Other 1

  • TI-2024-08981 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-09832 Use after free in Mozilla Firefox KEVCVSS 3.1CRITICAL 9.6
  • TI-2019-08769 Improper input validation in Mozilla Firefox ESR KEVCVSS 3.1CRITICAL 10.0
  • TI-2010-03577 Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before… KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-04799 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
  • TI-2023-04477 Out-of-bounds write in Google Chrome KEVCVSS 3.1HIGH 8.8
See all 3444 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences