medium 6.5

CVE-2025-5986 json

Unsolicited File Download, Disk Space Exhaustion, and Credential Leakage via mailbox:/// Links

published 2025-06-11 16 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-18099

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.6%; EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits: 0; none known

A crafted HTML email using mailbox:/// links can trigger automatic, unsolicited downloads of .pdf files to the user's desktop or home directory without prompting, even if auto-saving is disabled. This behavior can be abused to fill the disk with garbage data (e.g. using /dev/urandom on Linux) or to leak Windows credentials via SMB links when the email is viewed in HTML mode. While user interaction is required to download the .pdf file, visual obfuscation can conceal the download trigger. Viewing the email in HTML mode is enough to load external content. This vulnerability was fixed in Thunderbird 128.11.1 and Thunderbird 139.0.2.

Patch / fix

fixed in 2 distros 7

mozilla thunderbird 128.11.1, 139.0.2
mozilla thunderbird_esr 128.11.1, 139.0.2

debian ubuntu red hat suse opensuse almalinux rocky linux

thunderbird Debian 12 1:128.12.0esr-1~deb12u1
thunderbird Debian 14, Debian 13 1:128.12.0esr-1

debian advisories DEBIAN-CVE-2025-5986

thunderbird Ubuntu 22.04 LTS 1:128.12.0+build1-0ubuntu0.22.04.1

ubuntu advisories UBUNTU-CVE-2025-5986

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

thunderbird RHEL 8 128.12.0-1.el8_10
thunderbird RHEL 9 128.12.0-1.el9_6
thunderbird RHEL 10.0 128.12.0-1.el10_0
thunderbird RHEL 8.2 AUS 128.12.0-1.el8_2
thunderbird RHEL 8.4 AUS 128.12.0-1.el8_4
thunderbird RHEL 8.8 TUS, RHEL 8.8 E4S 128.12.0-1.el8_8
thunderbird RHEL 8.6 TUS, RHEL 8.6 E4S, RHEL 8.6 AUS 128.12.0-1.el8_6
thunderbird RHEL 9.2 E4S 128.12.0-1.el9_2

red hat advisories RHSA-2025:10246 RHSA-2025:10196 RHSA-2025:10195 RHSA-2025:10166 RHSA-2025:10165 RHSA-2025:10163

MozillaThunderbird SLE Workstation Extension 15 SP7, SLE Workstation Extension 15 SP6, SLE Module for Package Hub 15 SP7 +2 more 128.11.1-150200.8.224.1

suse advisories SUSE-SU-2025:02158-1

MozillaThunderbird openSUSE Tumbleweed 128.11.1-2.1

opensuse advisories openSUSE-SU-2025:15204-1

thunderbird AlmaLinux 10 128.12.0-1.el10_0.alma.1
thunderbird AlmaLinux 9 128.12.0-1.el9_6.alma.1
thunderbird AlmaLinux 8 128.12.0-1.el8_10.alma.1

almalinux advisories ALSA-2025:10195 ALSA-2025:10196 ALSA-2025:10246

thunderbird Rocky Linux 9 128.12.0-1.el9_6
thunderbird Rocky Linux 10 128.12.0-1.el10_0
thunderbird Rocky Linux 8 128.12.0-1.el8_10

rocky linux advisories RLSA-2025:10196 RLSA-2025:10195 RLSA-2025:10246

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-5986 updated 2026-11-04 cvss 6.5

thunderbird: Unsolicited File Download, Disk Space Exhaustion, and Credential Leakage via mailbox:/// Links

Red Hat Enterprise Linux 6 thunderbird Red Hat Enterprise Linux 7 thunderbird
affected: no fix planned “Out of support scope”
Red Hat Enterprise Linux 10 thunderbird-flatpak
affected: no fix available
Red Hat Enterprise Linux AppStream (v. 8) thunderbird 128.12.0-1.el8_10
fixed: vendor fix RHSA-2025:10246
Red Hat Enterprise Linux AppStream (v. 9) thunderbird 128.12.0-1.el9_6
fixed: vendor fix RHSA-2025:10196
Red Hat Enterprise Linux AppStream (v. 10) thunderbird 128.12.0-1.el10_0
fixed: vendor fix RHSA-2025:10195
Red Hat Enterprise Linux AppStream AUS (v. 8.2) thunderbird 128.12.0-1.el8_2
fixed: vendor fix RHSA-2025:10166
Red Hat Enterprise Linux AppStream AUS (v.8.4) thunderbird 128.12.0-1.el8_4
fixed: vendor fix RHSA-2025:10165
Red Hat Enterprise Linux AppStream AUS (v.8.6) thunderbird 128.12.0-1.el8_6 Red Hat Enterprise Linux AppStream E4S (v.8.6) thunderbird 128.12.0-1.el8_6
fixed: vendor fix RHSA-2025:10164

show 6 more

Red Hat Enterprise Linux AppStream E4S (v.8.8) thunderbird 128.12.0-1.el8_8
fixed: vendor fix RHSA-2025:10163
Red Hat Enterprise Linux AppStream E4S (v.9.0) thunderbird 128.12.0-1.el9_0
fixed: vendor fix RHSA-2025:10161
Red Hat Enterprise Linux AppStream E4S (v.9.2) thunderbird 128.12.0-1.el9_2
fixed: vendor fix RHSA-2025:10160
Red Hat Enterprise Linux AppStream EUS (v.9.4) thunderbird 128.12.0-1.el9_4
fixed: vendor fix RHSA-2025:10159
Red Hat Enterprise Linux AppStream TUS (v.8.6) thunderbird 128.12.0-1.el8_6
fixed: vendor fix RHSA-2025:10164
Red Hat Enterprise Linux AppStream TUS (v.8.8) thunderbird 128.12.0-1.el8_8
fixed: vendor fix RHSA-2025:10163

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 16 mo ago (2025-06-11)

Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CNA	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected products

Mozilla Thunderbird

Classification

Weakness

CWE-451 User Interface (UI) Misrepresentation of Critical Information

References

mozilla.org /security/advisories/mfsa2025-49/
vendor-advisory
mozilla.org /security/advisories/mfsa2025-50/
vendor-advisory
bugzilla.mozilla.org /buglist.cgi?bug_id=1958580%2C1968012
broken-link
lists.debian.org /debian-lts-announce/2025/07/msg00002.html

Sources

CVE List CVE-2025-5986
NVD CVE-2025-5986

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary