CVE-2025-4093 | Memory safety bug fixed in Firefox ESR 128.10 and Thunderbird 128.10

Memory safety bug present in Firefox ESR 128.9, and Thunderbird 128.9. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.10 and Thunderbird 128.10.

Published: 2025-04-29 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-4093 is rated Moderate Risk (47/100): CVSS High severity, with low exploitation likelihood (EPSS 0.20%). 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-2025-4093

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 2026-06-07 0.43% 0.20% -0.22%
2 2026-02-23 0.06% 0.43% +0.37%
3 2025-11-04 — 0.06% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-4093

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H 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:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-4093

OS Trackers for CVE-2025-4093

vendor priority summary link
alpine — CVE-2025-4093: 3 source package rows (firefox, firefox-esr, thunderbird); 327 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 327. https://security.alpinelinux.org/vuln/CVE-2025-4093
debian not yet assigned CVE-2025-4093 not yet assigned priority: Debian including 2 source packages (firefox-esr, thunderbird), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 10. https://security-tracker.debian.org/tracker/CVE-2025-4093
redhat high — https://access.redhat.com/security/cve/CVE-2025-4093
suse high CVE-2025-4093 severity important: SUSE including 18 source package names (MozillaFirefox-128.10.0-150200.152.179.1, MozillaFirefox-branding-upstream-128.10.0-150200.152.179.1, …), 100 product×package rows across 38 product lines (Container suse/kiosk/firefox-esr, Image SLES15-SP3-SAP-Azure-LI-BYOS-Production, … (38 product lines)): Fixed 100. https://www.suse.com/security/cve/CVE-2025-4093/
ubuntu medium CVE-2025-4093 medium priority: Ubuntu including 1 source packages (thunderbird), 6 status rows across 6 suites (focal, jammy, noble, oracular, plucky, upstream): not-affected 3, released 2, DNE 1. https://ubuntu.com/security/CVE-2025-4093

Affected software / configurations for CVE-2025-4093

Vendor Product Version Raw CPE
mozilla firefox < 128.10 cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
mozilla thunderbird < 128.10.0 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:esr:*:*:*

References for CVE-2025-4093

cvelogic Threat Intelligence