Description
When Eclipse Mosquitto version 1.0 to 1.5.5 (inclusive) is configured to use a password file for authentication, any malformed data in the password file will be treated as valid. This typically means that the malformed data becomes a username and no password. If this occurs, clients can circumvent authentication and get access to the broker by using the malformed username. In particular, a blank line will be treated as a valid empty username. Other security measures are unaffected. Users who have only used the mosquitto_passwd utility to create and modify their password files are unaffected by this vulnerability.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| The Eclipse Foundation | Eclipse Mosquitto | 1.0 – < unspecified, unspecified – ≤ 1.5.5 | unspecified |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | mosquitto | 1.5.6-1 | — |
| Debian 13 | mosquitto | 1.5.6-1 | — |
| Debian 12 | mosquitto | 1.5.6-1 | — |
| Debian 9 | mosquitto | 1.4.10-3+deb9u3 | DSA-4388-1 |
| Debian 8 | mosquitto | 1.3.4-2+deb8u4 | DLA-1972-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | mosquitto | 1.4.15-2ubuntu0.18.04.1 | — |
| Ubuntu 16.04 LTS | mosquitto | 1.4.8-1ubuntu0.16.04.5 | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SUSE Package Hub 15 | mosquitto | 1.4.15-bp150.3.3.1 | openSUSE-SU-2019:0237-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.23 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.22 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.21 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.20 | mosquitto | 1.5.6-r0 | — |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.18 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.17 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.16 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.15 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.14 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.13 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.12 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.11 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.10 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.9 | mosquitto | 1.5.6-r0 | — |
| Alpine v3.8 | mosquitto | 1.4.15-r4 | — |
| Alpine v3.7 | mosquitto | 1.4.15-r1 | — |
Advisories 3
- DSA-4388-1 mosquitto - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1972-1 mosquitto - security update Debian Security (DSA / DLA) · Mar 9, 2026
- openSUSE-SU-2019:0237-1 Security update for mosquitto SUSE / openSUSE Security Updates · Feb 4, 2026