CVE-2026-57963

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-07-01. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 4 sources updated this week
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content, phishing links, and CSS that manipulates the chat UI. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.

CVSS v3
6.5
EG Score
6.5(high)
EPSS
9.1%
KEV
Not listed

Published

July 1, 2026

Last Modified

July 6, 2026

Advisory Details (3)

Auto-updated Jul 3, 2026
No patch confirmed yet.
generic

Security Vulnerabilities fixed in Thunderbird 140.12.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-64/
generic

Security Vulnerabilities fixed in Thunderbird 152.0.1 — Mozilla

https://www.mozilla.org/security/advisories/mfsa2026-63/
generic

Access Denied

https://bugzilla.mozilla.org/show_bug.cgi?id=2042910

Vendor Advisories for CVE-2026-57963(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

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

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 20:38 UTCEG score recompute
  2. 2026-07-06 20:38 UTCGHSA enrichment
  3. 2026-07-06 16:27 UTCEPSS rescore
  4. 2026-07-06 16:27 UTCEPSS rescore
  5. 2026-07-06 02:23 UTCEPSS rescore
  6. 2026-07-06 02:23 UTCEPSS rescore
  7. 2026-07-05 20:52 UTCEG score recompute
  8. 2026-07-05 20:51 UTCGHSA enrichment
  9. 2026-07-05 02:31 UTCEPSS rescore
  10. 2026-07-05 02:30 UTCEPSS rescore
  11. 2026-07-04 21:01 UTCEG score recompute
  12. 2026-07-04 21:01 UTCGHSA enrichment
  13. 2026-07-04 06:31 UTCEPSS rescore
  14. 2026-07-04 06:31 UTCEPSS rescore
  15. 2026-07-03 21:15 UTCEG score recompute▲ 6.50
  16. 2026-07-03 21:15 UTCGHSA enrichment
  17. 2026-07-01 17:06 UTCNVD updateCVSS v3 → 6.5 · severity → MEDIUM
  18. 2026-07-01 15:07 UTCEPSS rescore
  19. 2026-07-01 03:20 UTCEG score recompute
  20. 2026-07-01 03:20 UTCNVD updatefirst tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-57963?
CVE-2026-57963 is a medium vulnerability published on July 1, 2026. An attacker who can send HTML chat messages (via Matrix or XMPP) can inject arbitrary styled content, phishing links, and CSS that manipulates the chat UI. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.
When was CVE-2026-57963 disclosed?
CVE-2026-57963 was first published in the National Vulnerability Database on July 1, 2026, with the most recent update on July 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-57963 actively exploited?
CVE-2026-57963 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 9.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-57963?
CVE-2026-57963 has a CVSS v3.1 base score of 6.5 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-57963?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-57963, 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

Explore the affected products and dependency analysis for CVE-2026-57963

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