Description
Persistent cross-site scripting (XSS) in http/cervlet.c in Tildeslash Monit before 5.25.3 allows a remote unauthenticated attacker to introduce arbitrary JavaScript via manipulation of an unsanitized user field of the Authorization header for HTTP Basic Authentication, which is mishandled during an _viewlog operation.
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 | monit | 1:5.25.3-1 | — |
| Debian 13 | monit | 1:5.25.3-1 | — |
| Debian 12 | monit | 1:5.25.3-1 | — |
| Debian 9 | monit | 1:5.20.0-6+deb9u2 | DLA-2855-1 |
| Debian 8 | monit | 1:5.9-1+deb8u2 | DLA-1767-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 18.04 LTS | monit | 1:5.25.1-1ubuntu0.1~esm1 | USN-4860-1 |
| Ubuntu Pro 16.04 LTS | monit | 1:5.16-2ubuntu0.2+esm1 | USN-4860-1 |
| Ubuntu Pro 14.04 LTS | monit | 1:5.6-2ubuntu0.1+esm2 | USN-4860-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.9 | monit | 5.25.2-r1 | — |
| Alpine v3.8 | monit | 5.25.2-r0 | — |
| Alpine v3.7 | monit | 5.24.0-r2 | — |
Advisories 3
- USN-4860-1 monit vulnerabilities Ubuntu Security Notices (USN) · Jun 29, 2026
- DLA-2855-1 monit - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-1767-1 monit - security update Debian Security (DSA / DLA) · Mar 9, 2026
References
- https://bitbucket.org/tildeslash/monit/commits/328f60773057641c4b2075fab9820145e95b728c
- https://bitbucket.org/tildeslash/monit/commits/1a8295eab6815072a18019b668fe084945b751f3
- https://github.com/dzflack/exploits/blob/master/unix/monit_xss.py
- [debian-lts-announce] 20190426 [SECURITY] [DLA 1767-1] monit security update mailing-list
- USN-3971-1 vendor-advisory
- FEDORA-2020-9c19202d55 vendor-advisory
- FEDORA-2020-f70cd7c24b vendor-advisory
- [debian-lts-announce] 20211227 [SECURITY] [DLA 2855-1] monit security update mailing-list