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TI-2020-16393 Aliases CVE-2020-26970GHSA-w8wp-h42w-f3m4

Out-of-bounds write in Mozilla Thunderbird

Priority MEDIUM 41CWE-787Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 7 fixed, 2 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-787 and the CVSS impact.

Summary

When reading SMTP server status codes, Thunderbird writes an integer value to a position on the stack that is intended to contain just one byte. Depending on processor architecture and stack layout, this leads to stack corruption that may be exploitable. This vulnerability affects Thunderbird < 78.5.1.

Why it matters now

EPSS 0.01247 69th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 78.5.1Red Hat: 5 advisoriesRed Hat: 7 fixed, 2 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaThunderbirdbefore 78.5.178.5.1Patch availableCNA
  • Thunderbird VendorMozilla Affected before 78.5.1 Fixed in 78.5.1 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*before 78.5.1VulnerableMozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* Versions before 78.5.1 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Thunderbird (Mozilla) Fixed in 78.5.1

Red Hat 5 advisories

  • RHSA-2020:5645 Released 2020-12-21 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v. 8.0) thunderbird-78.6.0-1.el8_0
  • RHSA-2020:5644 Released 2020-12-21 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.1) thunderbird-78.6.0-1.el8_1
  • RHSA-2020:5400 Released 2020-12-14 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux Client (v. 7) thunderbird-78.5.1-1.el7_9
    • Red Hat Enterprise Linux Server Optional (v. 7) thunderbird-78.5.1-1.el7_9
    • Red Hat Enterprise Linux Workstation (v. 7) thunderbird-78.5.1-1.el7_9
Show 2 more Red Hat advisories
  • RHSA-2020:5399 Released 2020-12-14 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 8.2) thunderbird-78.5.1-1.el8_2
  • RHSA-2020:5398 Released 2020-12-14 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-78.5.1-1.el8_3

Vendor assessments

Red Hat

Red Hat rating: Important. 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 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2020:5398
Red Hat Enterprise Linux AppStream E4S (v. 8.0)Fixed RHSA-2020:5645
Red Hat Enterprise Linux AppStream EUS (v. 8.1)Fixed RHSA-2020:5644
Red Hat Enterprise Linux AppStream EUS (v. 8.2)Fixed RHSA-2020:5399
Red Hat Enterprise Linux Client (v. 7)Fixed RHSA-2020:5400
Red Hat Enterprise Linux Server Optional (v. 7)Fixed RHSA-2020:5400
Red Hat Enterprise Linux Workstation (v. 7)Fixed RHSA-2020:5400

Timeline

  1. 2026-10-02 Threatist record created from CVE-2020-26970
  2. 2026-10-03 Alias added: GHSA-w8wp-h42w-f3m4

References

Advisory 2

  • 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 2067 →

Sources

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