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TI-2026-12554 Aliases CVE-2026-14899GHSA-6667-m7mf-jcr7

Off-by-one out of bounds read in MIME header parser for forwarding

Priority LOW 39CWE-193Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · None · None
Fix status
Partial Red Hat: 13 fixed, 3 without a fix

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

Summary

The code to parse MIME headers for display when forwarding a message (if the setting to view all headers was enabled) had an off-by-one error, allowing a single byte to be read from the memory after the buffer for the headers, and potentially crashing Thunderbird. This vulnerability was fixed in Thunderbird 153 and Thunderbird 140.13.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00469 40th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 140.13, 153Red Hat: 10 advisoriesRed Hat: 13 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

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

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaThunderbird—140.13, 153Patch availableCNA
  • Thunderbird VendorMozilla Affected — Fixed in 140.13, 153 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*before 140.13.0VulnerableMozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* Versions before 140.13.0 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Thunderbird (Mozilla) Fixed in 140.13, 153

Red Hat 10 advisories

  • RHSA-2026:53475 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird-140.13.0-1.el9_2
  • RHSA-2026:53454 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) thunderbird-140.13.0-1.el8_8
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird-140.13.0-1.el8_8
  • RHSA-2026:53453 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) thunderbird-140.13.0-1.el8_6
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) thunderbird-140.13.0-1.el8_6
Show 7 more Red Hat advisories
  • RHSA-2026:53455 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) thunderbird-140.13.0-1.el8_4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) thunderbird-140.13.0-1.el8_4
  • RHSA-2026:53446 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) thunderbird-140.13.0-1.el9_6
  • RHSA-2026:53444 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.4) thunderbird-140.13.0-1.el9_4
  • RHSA-2026:53445 Released 2026-08-11 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) thunderbird-140.13.0-1.el10_0
  • RHSA-2026:49921 Released 2026-08-04 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 9) thunderbird-140.13.0-1.el9_8
  • RHSA-2026:49922 Released 2026-08-04 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-140.13.0-1.el8_10
  • RHSA-2026:49621 Released 2026-08-03 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 10) thunderbird-140.13.0-1.el10_2

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:49621
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:49922
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:49921
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:53455
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:53453
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:53454
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:53475
Red Hat Enterprise Linux AppStream E4S (v.9.4)Fixed RHSA-2026:53444
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:53445
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:53446
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:53455
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)Fixed RHSA-2026:53453
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:53454

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-14899
  2. 2026-10-03 Alias added: GHSA-6667-m7mf-jcr7

References

Advisory 2

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 2067 →

Sources

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