CVE-2025-3523 | User Interface (UI) Misrepresentation of attachment URL

When an email contains multiple attachments with external links via the X-Mozilla-External-Attachment-URL header, only the last link is shown when hovering over any attachment. Although the correct link is used on click, the misleading hover text could trick users into downloading content from untrusted sources. This vulnerability was fixed in Thunderbird 137.0.2 and Thunderbird 128.9.2.

Published: 2025-04-15 Last update: 2026-04-13 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-3523 is rated Low Risk (35.3/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.11%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

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-2025-3523

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 2026-05-24 0.24% 0.11% -0.14%
2 2026-03-04 0.30% 0.24% -0.05%
3 2026-02-09 — 0.30% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-3523

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:H/A:L 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: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:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 1.6 4.7 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-3523

OS Trackers for CVE-2025-3523

vendor priority summary link
alpine — CVE-2025-3523: 1 source package rows (thunderbird); 68 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 68. https://security.alpinelinux.org/vuln/CVE-2025-3523
debian not yet assigned CVE-2025-3523 not yet assigned priority: Debian including 1 source packages (thunderbird), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2025-3523
redhat low — https://access.redhat.com/security/cve/CVE-2025-3523
suse high CVE-2025-3523 severity important: SUSE including 15 source package names (MozillaFirefox, MozillaFirefox-branding-upstream, …), 90 product×package rows across 27 product lines (SLES-LTSS-TERADATA 15 SP2, SUSE Liberty Linux 8, … (27 product lines)): Known Not Affected 75, Fixed 15. https://www.suse.com/security/cve/CVE-2025-3523/
ubuntu medium CVE-2025-3523 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-2025-3523

Affected software / configurations for CVE-2025-3523

Vendor Product Version Raw CPE
mozilla thunderbird < 128.9.2 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
mozilla thunderbird >= 129.0, < 137.0.2 cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

References for CVE-2025-3523

cvelogic Threat Intelligence