CVE-2026-2777

CRITICALNVD 9.89.8—

9.8

Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 20.9%
KEV: Not listed

Published

February 24, 2026

Last Modified

April 13, 2026

Advisory Details (6)

Auto-updated May 20, 2026

No patch confirmed yet.

generic

Security Vulnerabilities fixed in Thunderbird 140.8 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-17/

generic

Security Vulnerabilities fixed in Thunderbird 148 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-16/

generic

Security Vulnerabilities fixed in Firefox ESR 140.8 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-15/

generic

Security Vulnerabilities fixed in Firefox ESR 115.33 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-14/

generic

Security Vulnerabilities fixed in Firefox 148 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-13/

generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2015305

Patch Availability(25)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
redhat	thunderbird-0:140.8.0-1.el8_2	2026-03-12	redhat
redhat	thunderbird-0:140.8.0-2.el10_0	2026-03-11	redhat
redhat	firefox-0:140.8.0-2.el9_2	2026-03-10	redhat
redhat	thunderbird-0:140.8.0-2.el8_4	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-1.el8_6	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-1.el9_2	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-1.el9_4	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-1.el8_8	2026-03-09	redhat
redhat	firefox-0:140.8.0-2.el10_0	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-1.el9_6	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-1.el9_0	2026-03-09	redhat
redhat	firefox-0:140.8.0-2.el7_9	2026-03-09	redhat
redhat	thunderbird-0:140.8.0-2.el10_1	2026-03-02	redhat
redhat	thunderbird-0:140.8.0-1.el8_10	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el9_4	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el9_6	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el8_4	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el8_2	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el8_6	2026-03-02	redhat
redhat	thunderbird-0:140.8.0-1.el9_7	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el8_8	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el9_0	2026-03-02	redhat
redhat	firefox-0:140.8.0-2.el9_7	2026-02-25	redhat
redhat	firefox-0:140.8.0-2.el10_1	2026-02-25	redhat
redhat	firefox-0:140.8.0-2.el8_10	2026-02-25	redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

All Vendor Advisories

(25)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 15× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-31 22:30 UTCepss_batch
2026-05-31 22:30 UTCepss_batch
2026-05-29 13:44 UTCepss_batch
2026-05-29 13:44 UTCepss_batch
2026-05-28 13:44 UTCepss_batch
2026-05-28 13:44 UTCepss_batch
2026-05-28 13:44 UTCepss_batch
2026-05-27 13:40 UTCepss_batch
2026-05-27 13:40 UTCepss_batch
2026-05-27 13:40 UTCepss_batch
2026-05-26 13:44 UTCepss_batch
2026-05-26 13:44 UTCepss_batch
2026-05-26 07:18 UTCepss_batch
2026-05-26 07:18 UTCepss_batch
2026-05-26 07:18 UTCepss_batch
2026-05-24 16:59 UTCepss_batch
2026-05-23 15:21 UTCepss_batch
2026-05-22 21:16 UTCepss_batch
2026-05-20 22:38 UTCepss_batch
2026-05-20 22:38 UTCepss_batch

Frequently asked(5)

What is CVE-2026-2777?

CVE-2026-2777 is a critical vulnerability published on February 24, 2026. Privilege escalation in the Messaging System component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.

When was CVE-2026-2777 disclosed?

CVE-2026-2777 was first published in the National Vulnerability Database on February 24, 2026, with the most recent update on April 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2026-2777 actively exploited?

CVE-2026-2777 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 20.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2026-2777?

CVE-2026-2777 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2026-2777?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-2777, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2026-2777

📅 Published

🔄 Last Modified

📋 Advisory Details (6)

Security Vulnerabilities fixed in Thunderbird 140.8 — Mozilla

Security Vulnerabilities fixed in Thunderbird 148 — Mozilla

Security Vulnerabilities fixed in Firefox ESR 140.8 — Mozilla

Security Vulnerabilities fixed in Firefox ESR 115.33 — Mozilla

Security Vulnerabilities fixed in Firefox 148 — Mozilla

Access Denied

Patch Availability(25)

All Vendor Advisories

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2026-2777?

🔗 Related CVEs(same vendor)

Same vendor

Published

Last Modified

Advisory Details (6)

Frequently asked(5)

Related CVEs(same vendor)