What is CVE-2020-26547?

CVE-2020-26547 is a critical-severity vulnerability in Monal, classified under Insufficient Verification of Data Authenticity. CVSS score: 9.8/10. Published 2021-02-01.

How severe is CVE-2020-26547?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Monal

CVE-2020-26547

Monal before 4.9 does not implement proper sender verification on MAM and Message Carbon (XEP-0280) results. This allows a remote attacker (able to send stanzas to a victim) to inject arbitrary messages into the local history, with full control over the sender and receiver displayed to the victim.

Published 2021-02-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (43.8th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 43.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Monal

Weakness classification (CWE)

CWE-345 — Insufficient Verification of Data Authenticity

References

github.com/anurodhp/Monal/commits/develop (Third Party Advisory)
monal.im/blog/cve-2020-26547/ (Vendor Advisory)

Frequently asked questions

What is CVE-2020-26547?: CVE-2020-26547 is a critical-severity vulnerability in Monal, classified under Insufficient Verification of Data Authenticity. CVSS score: 9.8/10. Published 2021-02-01.
How severe is CVE-2020-26547?: Critical severity. CVSS v3 base score is 9.8 out of 10.