CVE-2025-0239

MEDIUMNVD 4.04.0—
EchelonGraph scoreMEDIUM confidence

Score 4.0 from GitHub Security Advisory published 2025-01-07. NVD baseline CVSS 4.0; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
4.0
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.0Exploit: NoneExposed: 0

A fix is available — apply it.

When using Alt-Svc, ALPN did not properly validate certificates when the original server is redirecting to an insecure site. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.

CVSS v3
4.0
EG Score
4.0(medium)
EG Risk
18(Track)
EG Risk 18/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity40% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
13.5%
KEV
Not listed

Published

January 7, 2025

Last Modified

April 13, 2026

References (6)

Patch Availability(21)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntufirefox-mozsymbols (134.0+build1-0ubuntu0.20.04.1) @ focal2026-05-21ubuntu
ubuntuxul-ext-lightning (1:140.7.1+build1-0ubuntu0.22.04.1) @ jammy2026-05-21ubuntu
redhatthunderbird-0:128.6.0-3.el8_42025-01-13redhat
redhatthunderbird-0:128.6.0-3.el8_82025-01-13redhat
redhatthunderbird-0:128.6.0-3.el8_22025-01-13redhat
redhatthunderbird-0:128.6.0-3.el8_102025-01-13redhat
redhatthunderbird-0:128.6.0-3.el8_62025-01-13redhat
redhatfirefox-0:128.6.0-1.el9_22025-01-09redhat
redhatthunderbird-0:128.6.0-3.el9_22025-01-09redhat
redhatthunderbird-0:128.6.0-3.el9_52025-01-09redhat
redhatfirefox-0:128.6.0-1.el8_42025-01-09redhat
redhatfirefox-0:128.6.0-1.el9_02025-01-09redhat
redhatfirefox-0:128.6.0-1.el7_92025-01-09redhat
redhatthunderbird-0:128.6.0-3.el9_42025-01-09redhat
redhatfirefox-0:128.6.0-1.el8_102025-01-09redhat
redhatfirefox-0:128.6.0-1.el8_22025-01-09redhat
redhatfirefox-0:128.6.0-1.el8_82025-01-09redhat
redhatfirefox-0:128.6.0-1.el9_42025-01-09redhat
redhatthunderbird-0:128.6.0-3.el9_02025-01-09redhat
redhatfirefox-0:128.6.0-1.el8_62025-01-09redhat
redhatfirefox-0:128.6.0-1.el9_52025-01-08redhat

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.

All Vendor Advisories

(21)

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 9× in last 7d / 44× 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.

Showing the most recent 100 of 123 total refreshes for this CVE.

  1. 2026-07-23 14:17 UTCEPSS rescore
  2. 2026-07-23 02:47 UTCEG score recompute
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Frequently asked(5)

What is CVE-2025-0239?
CVE-2025-0239 is a medium vulnerability published on January 7, 2025. When using Alt-Svc, ALPN did not properly validate certificates when the original server is redirecting to an insecure site. This vulnerability was fixed in Firefox 134, Firefox ESR 128.6, Thunderbird 134, and Thunderbird 128.6.
When was CVE-2025-0239 disclosed?
CVE-2025-0239 was first published in the National Vulnerability Database on January 7, 2025, 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-2025-0239 actively exploited?
CVE-2025-0239 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 13.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2025-0239?
CVE-2025-0239 has a CVSS v3 base score of 4.0 (NVD).
How do I remediate CVE-2025-0239?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2025-0239, 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-2025-0239

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