CVE-2026-21888 json
MQTT v5 Variable Byte Integer parsing out-of-bounds: get_var_integer()
published 7mo ago modified 4mo ago also EUVD-2026-11190
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 28%
- public exploits
- 0
- none known
Summary
NanoMQ MQTT Broker (NanoMQ) is an all-around Edge Messaging Platform. MQTT v5 Variable Byte Integer parsing out-of-bounds: get_var_integer() accepts 5-byte varints without bounds checks; reliably triggers OOB read / crash when built with ASan. This affects 0.24.6 and earlier.
Patch / fix
- emqx nanomq 0.24.7
Is CVE-2026-21888 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 7mo ago
Exploit prediction
0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- github.com https://github.com/nanomq/nanomq/security/advisories/GHSA-cggc-6m7w-j7x5 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected products
- nanomq nanomq
Classification
- Weakness
-
- CWE-125 Out-of-bounds Read
References
-
github.com
/nanomq/nanomq/security/advisories/GHSA-cggc-6m7w-j7x5
exploit, vendor-advisory
-
github.com
/nanomq/nanomq/issues/2192
issue-tracking
Sources
- CVE List CVE-2026-21888
- NVD CVE-2026-21888
Fencer Intel 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.