CVE-2025-1943 | Memory safety bugs fixed in Firefox 136 and Thunderbird 136

Memory safety bugs present in Firefox 135 and Thunderbird 135. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 136 and Thunderbird 136.

Published: 2025-03-04 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-1943 is rated Moderate Risk (53.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.36%). 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-2025-1943

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 2026-04-12 0.27% 0.36% +0.09%
2 2025-11-28 0.24% 0.27% +0.03%
3 2025-11-21 — 0.24% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-1943

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.2 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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: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: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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 4.2 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-1943

OS Trackers for CVE-2025-1943

vendor priority summary link
alpine — CVE-2025-1943: 2 source package rows (firefox, thunderbird); 200 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 200. https://security.alpinelinux.org/vuln/CVE-2025-1943
debian not yet assigned CVE-2025-1943 not yet assigned priority: Debian including 1 source packages (firefox), 1 status rows across 1 suites (sid): resolved 1. https://security-tracker.debian.org/tracker/CVE-2025-1943
gentoo high CVE-2025-1943: 1 GLSA(s) (202505-02), 2 atom(s) (www-client/firefox, www-client/firefox-bin); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2025-1943
redhat high — https://access.redhat.com/security/cve/CVE-2025-1943
ubuntu medium CVE-2025-1943 medium priority: Ubuntu including 9 source packages (firefox, mozjs102, …), 65 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): DNE 34, ignored 10, not-affected 9, needs-triage 8, released 4. https://ubuntu.com/security/CVE-2025-1943

Affected software / configurations for CVE-2025-1943

Vendor Product Version Raw CPE
mozilla firefox < 136.0 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
mozilla thunderbird < 136.0 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

References for CVE-2025-1943

cvelogic Threat Intelligence