9.8
CRITICAL
CVSS 3.1
CVE-2026-74987
Internally found bugs fixed in Thunderbird ESR 140.14, Thunderbird ESR 153.1 and Thunderbird 154
Overview
Description
Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
Details
INFO
Published Date :
Aug. 18, 2026, 1:17 p.m.
Last Modified :
Sept. 1, 2026, 10:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework
for assessing the severity of vulnerabilities in software and systems.
We collect and displays CVSS scores from various sources for each CVE.
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
Update Firefox and Firefox ESR to the latest versions to fix memory corruption vulnerabilities.
- Update Firefox ESR to version 140.14 or later.
- Update Firefox ESR to version 153.1 or later.
- Update Firefox to version 154 or later.
References
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-74987.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-74987 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-74987
weaknesses.
CAPEC-8: Buffer Overflow in an API Call Buffer Overflow in an API Call
CAPEC-9: Buffer Overflow in Local Command-Line Utilities Buffer Overflow in Local Command-Line Utilities
CAPEC-10: Buffer Overflow via Environment Variables Buffer Overflow via Environment Variables
CAPEC-14: Client-side Injection-induced Buffer Overflow Client-side Injection-induced Buffer Overflow
CAPEC-24: Filter Failure through Buffer Overflow Filter Failure through Buffer Overflow
CAPEC-42: MIME Conversion MIME Conversion
CAPEC-44: Overflow Binary Resource File Overflow Binary Resource File
CAPEC-45: Buffer Overflow via Symbolic Links Buffer Overflow via Symbolic Links
CAPEC-46: Overflow Variables and Tags Overflow Variables and Tags
CAPEC-47: Buffer Overflow via Parameter Expansion Buffer Overflow via Parameter Expansion
CAPEC-100: Overflow Buffers Overflow Buffers
CAPEC-123: Buffer Manipulation Buffer Manipulation
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-74987 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-74987 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by [email protected]
Sep. 01, 2026
Action Type Old Value New Value Changed Description Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. Added Reference https://bugzilla.mozilla.org/buglist.cgi?bug_id=1500946%2C1788109%2C2045379%2C2045380%2C2049339%2C2049393%2C2053580%2C2054662%2C2054665%2C2054673%2C2054785%2C2058645 Added Reference https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048797%2C2050536%2C2053272%2C2053579%2C2057115%2C2057116%2C2057130%2C2057991%2C2057995%2C2058002%2C2058008%2C2058032%2C2058102%2C2058667 Added Reference https://bugzilla.mozilla.org/show_bug.cgi?id=2059424 Added Reference https://www.mozilla.org/security/advisories/mfsa2026-74/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-76/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-77/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-78/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-79/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-80/ Removed Reference https://bugzilla.mozilla.org/buglist.cgi?bug_id=1500946%2C1788109%2C2045379%2C2045380%2C2049339%2C2049393%2C2053580%2C2054662%2C2054665%2C2054673%2C2054785%2C2058645 Removed Reference https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048797%2C2050536%2C2053272%2C2053579%2C2057115%2C2057116%2C2057130%2C2057991%2C2057995%2C2058002%2C2058008%2C2058032%2C2058102%2C2058667 Removed Reference https://bugzilla.mozilla.org/show_bug.cgi?id=2059424 Removed Reference https://www.mozilla.org/security/advisories/mfsa2026-74/ Removed Reference https://www.mozilla.org/security/advisories/mfsa2026-76/ Removed Reference https://www.mozilla.org/security/advisories/mfsa2026-77/ Removed Reference https://www.mozilla.org/security/advisories/mfsa2026-78/ Removed Reference https://www.mozilla.org/security/advisories/mfsa2026-79/ Removed Reference https://www.mozilla.org/security/advisories/mfsa2026-80/ Removed Reference Type https://bugzilla.mozilla.org/buglist.cgi?bug_id=1500946%2C1788109%2C2045379%2C2045380%2C2049339%2C2049393%2C2053580%2C2054662%2C2054665%2C2054673%2C2054785%2C2058645 Types: Broken Link Removed Reference Type https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048797%2C2050536%2C2053272%2C2053579%2C2057115%2C2057116%2C2057130%2C2057991%2C2057995%2C2058002%2C2058008%2C2058032%2C2058102%2C2058667 Types: Broken Link Removed Reference Type https://bugzilla.mozilla.org/show_bug.cgi?id=2059424 Types: Permissions Required Removed Reference Type https://www.mozilla.org/security/advisories/mfsa2026-74/ Types: Vendor Advisory Removed Reference Type https://www.mozilla.org/security/advisories/mfsa2026-76/ Types: Vendor Advisory Removed Reference Type https://www.mozilla.org/security/advisories/mfsa2026-77/ Types: Vendor Advisory Removed Reference Type https://www.mozilla.org/security/advisories/mfsa2026-78/ Types: Vendor Advisory Removed Reference Type https://www.mozilla.org/security/advisories/mfsa2026-79/ Types: Vendor Advisory Removed Reference Type https://www.mozilla.org/security/advisories/mfsa2026-80/ Types: Vendor Advisory -
CVE Modified by [email protected]
Aug. 24, 2026
Action Type Old Value New Value Changed Description Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. -
Initial Analysis by [email protected]
Aug. 19, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* versions from (including) 141.0 up to (excluding) 153.1.0 *cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* versions from (including) 141.0 up to (excluding) 153.1.0 *cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* versions up to (excluding) 140.14.0 *cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* versions up to (excluding) 140.14.0 Added Reference Type Mozilla Corporation: https://bugzilla.mozilla.org/buglist.cgi?bug_id=1500946%2C1788109%2C2045379%2C2045380%2C2049339%2C2049393%2C2053580%2C2054662%2C2054665%2C2054673%2C2054785%2C2058645 Types: Broken Link Added Reference Type Mozilla Corporation: https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048797%2C2050536%2C2053272%2C2053579%2C2057115%2C2057116%2C2057130%2C2057991%2C2057995%2C2058002%2C2058008%2C2058032%2C2058102%2C2058667 Types: Broken Link Added Reference Type Mozilla Corporation: https://bugzilla.mozilla.org/show_bug.cgi?id=2059424 Types: Permissions Required Added Reference Type Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-74/ Types: Vendor Advisory Added Reference Type Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-76/ Types: Vendor Advisory Added Reference Type Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-77/ Types: Vendor Advisory Added Reference Type Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-78/ Types: Vendor Advisory Added Reference Type Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-79/ Types: Vendor Advisory Added Reference Type Mozilla Corporation: https://www.mozilla.org/security/advisories/mfsa2026-80/ Types: Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 19, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE CWE-119 Added SSVC {'id': 'CVE-2026-74987', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-08-19T13:05:41.543564Z'} -
CVE Modified by [email protected]
Aug. 18, 2026
Action Type Old Value New Value Changed Affected [{'vendor': 'Mozilla', 'product': 'Firefox', 'versions': [{'status': 'unaffected', 'version': '140.14', 'versionType': 'rpm', 'lessThanOrEqual': '140.*'}, {'status': 'unaffected', 'version': '153.1', 'versionType': 'rpm', 'lessThanOrEqual': '153.*'}, {'status': 'unaffected', 'version': '154', 'versionType': 'rpm', 'lessThanOrEqual': '*'}]}] [{'vendor': 'Mozilla', 'product': 'Firefox', 'versions': [{'status': 'unaffected', 'version': '140.14', 'versionType': 'rpm', 'lessThanOrEqual': '140.*'}, {'status': 'unaffected', 'version': '153.1', 'versionType': 'rpm', 'lessThanOrEqual': '153.*'}, {'status': 'unaffected', 'version': '154', 'versionType': 'rpm', 'lessThanOrEqual': '*'}]}, {'vendor': 'Mozilla', 'product': 'Thunderbird', 'versions': [{'status': 'unaffected', 'version': '140.14', 'versionType': 'rpm', 'lessThanOrEqual': '140.*'}, {'status': 'unaffected', 'version': '153.1', 'versionType': 'rpm', 'lessThanOrEqual': '153.*'}, {'status': 'unaffected', 'version': '154', 'versionType': 'rpm', 'lessThanOrEqual': '*'}]}] Changed Description Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1. Internally found bugs present in Thunderbird ESR 140.13, Thunderbird ESR 153.0 and Thunderbird 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1. Added Reference https://www.mozilla.org/security/advisories/mfsa2026-78/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-79/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-80/ -
New CVE Received by [email protected]
Aug. 18, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Mozilla', 'product': 'Firefox', 'versions': [{'status': 'unaffected', 'version': '140.14', 'versionType': 'rpm', 'lessThanOrEqual': '140.*'}, {'status': 'unaffected', 'version': '153.1', 'versionType': 'rpm', 'lessThanOrEqual': '153.*'}, {'status': 'unaffected', 'version': '154', 'versionType': 'rpm', 'lessThanOrEqual': '*'}]}] Added Description Internally found bugs present in Firefox ESR 140.13, Firefox ESR 153.0 and Firefox 153. Some of these bugs showed evidence of memory corruption or another security-relevant defect and we presume that with enough effort some of these could have been exploited. This vulnerability was fixed in Firefox 154, Firefox ESR 140.14, and Firefox ESR 153.1. Added Reference https://bugzilla.mozilla.org/buglist.cgi?bug_id=1500946%2C1788109%2C2045379%2C2045380%2C2049339%2C2049393%2C2053580%2C2054662%2C2054665%2C2054673%2C2054785%2C2058645 Added Reference https://bugzilla.mozilla.org/buglist.cgi?bug_id=2048797%2C2050536%2C2053272%2C2053579%2C2057115%2C2057116%2C2057130%2C2057991%2C2057995%2C2058002%2C2058008%2C2058032%2C2058102%2C2058667 Added Reference https://bugzilla.mozilla.org/show_bug.cgi?id=2059424 Added Reference https://www.mozilla.org/security/advisories/mfsa2026-74/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-76/ Added Reference https://www.mozilla.org/security/advisories/mfsa2026-77/
EPSS is a daily estimate of the probability of exploitation activity
being observed over the next 30 days. Following chart shows the EPSS
score history of the vulnerability.