CVE-2025-6429 | Incorrect parsing of URLs could have allowed embedding of youtube.com

Firefox could have incorrectly parsed a URL and rewritten it to the youtube.com domain when parsing the URL specified in an `embed` tag. This could have bypassed website security checks that restricted which domains users were allowed to embed. This vulnerability was fixed in Firefox 140, Firefox ESR 128.12, Thunderbird 140, and Thunderbird 128.12.

Published: 2025-06-24 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-6429 is rated Moderate Risk (48.3/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.43%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-6429

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-04-20 0.06% 0.43% +0.38%
2 2025-12-02 0.04% 0.06% +0.01%
3 2025-11-21 — 0.04% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-6429

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-6429

OS Trackers for CVE-2025-6429

vendor priority summary link
alpine — CVE-2025-6429: 3 source package rows (firefox, firefox-esr, thunderbird); 372 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 372. https://security.alpinelinux.org/vuln/CVE-2025-6429
debian not yet assigned CVE-2025-6429 not yet assigned priority: Debian including 3 source packages (firefox, firefox-esr, thunderbird), 11 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 11. https://security-tracker.debian.org/tracker/CVE-2025-6429
redhat medium — https://access.redhat.com/security/cve/CVE-2025-6429
suse high CVE-2025-6429 severity important: SUSE including 80 source package names (2.1.3-4.11:qemu-guest-agent-8.2.7-1.1, MozillaFirefox-140.0-112.270.2, …), 361 product×package rows across 47 product lines (Container suse/sl-micro/6.0/kvm-os-container, Image SLES12-SP5-SAP-Azure-LI-BYOS-Production, … (47 product lines)): Fixed 358, First Fixed 3. https://www.suse.com/security/cve/CVE-2025-6429/
ubuntu medium CVE-2025-6429 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 58 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 28, ignored 10, needs-triage 9, not-affected 9, released 2. https://ubuntu.com/security/CVE-2025-6429

Affected software / configurations for CVE-2025-6429

Vendor Product Version Raw CPE
mozilla firefox < 128.12.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla firefox < 140.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*

References for CVE-2025-6429

cvelogic Threat Intelligence