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TI-2026-03807 Aliases CVE-2026-4371GHSA-4p49-pghr-968w

Out of bounds read in IMAP parsing

Priority LOW 33CWE-126Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · None · High
Fix status
Partial Red Hat: 16 fixed, 3 without a fix

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

Summary

A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00367 30th percentileScored 2026-11-07
Fix Partial Thunderbird (Mozilla): 140.9, 149Red Hat: 12 advisoriesRed Hat: 16 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
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—140.9, 149Patch availableCNA
  • Thunderbird VendorMozilla Affected — Fixed in 140.9, 149 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*before 140.9.0VulnerableMozilla
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:*before 149.0VulnerableMozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:* Versions before 140.9.0 Vulnerable ·Mozilla
  • cpe:2.3:a:mozilla:thunderbird:*:*:*:*:-:*:*:* Versions before 149.0 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Thunderbird (Mozilla) Fixed in 140.9, 149

Red Hat 12 advisories

  • RHSA-2026:8850 Released 2026-04-20 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.4) thunderbird-140.9.0-1.el8_4
    • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) thunderbird-140.9.0-1.el8_4
  • RHSA-2026:8315 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) thunderbird-140.9.0-1.el10_0
  • RHSA-2026:8290 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.4) thunderbird-140.9.0-1.el9_4
Show 9 more Red Hat advisories
  • RHSA-2026:8284 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) thunderbird-140.9.0-1.el9_6
  • RHSA-2026:8289 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v.8.6) thunderbird-140.9.0-1.el8_6
    • Red Hat Enterprise Linux AppStream E4S (v.8.6) thunderbird-140.9.0-1.el8_6
    • Red Hat Enterprise Linux AppStream TUS (v.8.6) thunderbird-140.9.0-1.el8_6
  • RHSA-2026:8286 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.0) thunderbird-140.9.0-1.el9_0
  • RHSA-2026:8287 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird-140.9.0-1.el9_2
  • RHSA-2026:8288 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream E4S (v.8.8) thunderbird-140.9.0-1.el8_8
    • Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird-140.9.0-1.el8_8
  • RHSA-2026:8285 Released 2026-04-15 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream AUS (v. 8.2) thunderbird-140.9.0-1.el8_2
  • RHSA-2026:6917 Released 2026-04-07 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 8) thunderbird-140.9.0-1.el8_10
  • RHSA-2026:6342 Released 2026-04-01 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 10) thunderbird-140.9.0-1.el10_1
  • RHSA-2026:6188 Released 2026-03-30 · Red Hat rating Important
    thunderbird security update
    • Red Hat Enterprise Linux AppStream (v. 9) thunderbird-140.9.0-1.el9_7

Vendor assessments

Red Hat

Red Hat rating: Important. 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-2026:6342
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2026:6917
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:6188
Red Hat Enterprise Linux AppStream AUS (v. 8.2)Fixed RHSA-2026:8285
Red Hat Enterprise Linux AppStream AUS (v.8.4)Fixed RHSA-2026:8850
Red Hat Enterprise Linux AppStream AUS (v.8.6)Fixed RHSA-2026:8289
Red Hat Enterprise Linux AppStream E4S (v.8.6)Fixed RHSA-2026:8289
Red Hat Enterprise Linux AppStream E4S (v.8.8)Fixed RHSA-2026:8288
Red Hat Enterprise Linux AppStream E4S (v.9.0)Fixed RHSA-2026:8286
Red Hat Enterprise Linux AppStream E4S (v.9.2)Fixed RHSA-2026:8287
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:8315
Red Hat Enterprise Linux AppStream EUS (v.9.4)Fixed RHSA-2026:8290
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:8284
Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4)Fixed RHSA-2026:8850
Red Hat Enterprise Linux AppStream TUS (v.8.6)Fixed RHSA-2026:8289
Red Hat Enterprise Linux AppStream TUS (v.8.8)Fixed RHSA-2026:8288

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-4371
  2. 2026-10-03 Alias added: GHSA-4p49-pghr-968w
  3. 2026-10-21 EPSS moved to the 50th–90th percentile
  4. 2026-10-25 EPSS moved to the below the 50th percentile

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