Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
CVE-2026-8950
CRITICALNVD 9.39.3—
EchelonGraph scoreMEDIUM confidence
Score 9.3 from GitHub Security Advisory (severity: CRITICAL) published 2026-05-19. NVD baseline CVSS 9.3; sources differ by 0.0.
Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
9.3
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.3Exploit: NoneExposed: 0
A fix is available — apply it.
- CVSS v3
- 9.3
- EG Score
- 9.3(medium)
- EPSS
- 9.3%
- KEV
- Not listed
Published
May 19, 2026
Last Modified
May 20, 2026
Advisory Details (5)
Auto-updated May 19, 2026No patch confirmed yet.
generic
Security Vulnerabilities fixed in Thunderbird 140.11 — Mozilla
https://www.mozilla.org/security/advisories/mfsa2026-51/generic
Security Vulnerabilities fixed in Thunderbird 151 — Mozilla
https://www.mozilla.org/security/advisories/mfsa2026-50/generic
Security Vulnerabilities fixed in Firefox ESR 140.11 — Mozilla
https://www.mozilla.org/security/advisories/mfsa2026-48/generic
Security Vulnerabilities fixed in Firefox 151 — Mozilla
https://www.mozilla.org/security/advisories/mfsa2026-46/Vendor Advisories for CVE-2026-8950(20)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:26630Red Hat Product SecurityHigh
Red Hat Security Advisory: firefox security update
- RHSA-2026:26629Red Hat Product SecurityHigh
Red Hat Security Advisory: firefox security update
- RHSA-2026:26606Red Hat Product SecurityHigh
Red Hat Security Advisory: firefox security update
- RHSA-2026:26551Red Hat Product SecurityHigh
Red Hat Security Advisory: firefox security update
- RHSA-2026:26539Red Hat Product SecurityHigh
Red Hat Security Advisory: thunderbird security update
- RHSA-2026:26536Red Hat Product SecurityHigh
Red Hat Security Advisory: thunderbird security update
- RHSA-2026:26521Red Hat Product SecurityHigh
Red Hat Security Advisory: thunderbird security update
- RHSA-2026:26492Red Hat Product SecurityHigh
Red Hat Security Advisory: firefox security update
- +12 more
Patch Availability(21)
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.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Additional Vendor Advisories
(1)
Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.
Frequently asked(5)
What is CVE-2026-8950?
CVE-2026-8950 is a critical vulnerability published on May 19, 2026. Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
When was CVE-2026-8950 disclosed?
CVE-2026-8950 was first published in the National Vulnerability Database on May 19, 2026, with the most recent update on May 20, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-8950 actively exploited?
CVE-2026-8950 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 9.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-8950?
CVE-2026-8950 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-8950?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-8950, 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-2026-8950
Is Your Infrastructure Affected by CVE-2026-8950?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.