CVE-2026-21888

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 77% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
7.5
EG Score
7.5(medium)
EG Risk
38(Track)
EG Risk 38/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity75% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
23%
KEV
Not listed

Published

March 11, 2026

Last Modified

June 17, 2026

Advisory Details (2)

Auto-updated Aug 2, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

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 · Advisory · nanomq/nanomq · GitHub

https://github.com/nanomq/nanomq/security/advisories/GHSA-cggc-6m7w-j7x5
generic

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 · Issue #2192 · nanomq/nanomq · GitHub

https://github.com/nanomq/nanomq/issues/2192

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 4× in last 7d / 23× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-09-18 19:27 UTCEPSS rescore
  2. 2026-09-16 14:07 UTCEPSS rescore
  3. 2026-09-16 05:15 UTCEPSS rescore
  4. 2026-09-13 16:47 UTCEPSS rescore
  5. 2026-09-12 15:01 UTCEPSS rescore
  6. 2026-09-11 14:52 UTCEPSS rescore
  7. 2026-09-10 09:34 UTCEPSS rescore
  8. 2026-09-08 22:00 UTCEPSS rescore
  9. 2026-09-06 13:47 UTCEPSS rescore
  10. 2026-09-06 13:47 UTCEPSS rescore
  11. 2026-09-04 05:06 UTCEPSS rescore
  12. 2026-09-02 20:10 UTCOSV refresh
  13. 2026-09-02 14:11 UTCEPSS rescore
  14. 2026-09-01 13:53 UTCEPSS rescore
  15. 2026-09-01 04:39 UTCEPSS rescore
  16. 2026-08-30 19:17 UTCEPSS rescore
  17. 2026-08-30 01:22 UTCEPSS rescore
  18. 2026-08-28 21:41 UTCEPSS rescore
  19. 2026-08-27 14:25 UTCEPSS rescore
  20. 2026-08-26 14:46 UTCEPSS rescore
  21. 2026-08-25 13:48 UTCEPSS rescore
  22. 2026-08-23 00:19 UTCEPSS rescore
  23. 2026-08-21 23:49 UTCEPSS rescore
  24. 2026-08-20 22:55 UTCEPSS rescore
  25. 2026-08-19 17:03 UTCEPSS rescore
Show 33 more
  1. 2026-08-18 13:48 UTCEPSS rescore
  2. 2026-08-17 13:47 UTCEPSS rescore
  3. 2026-08-16 14:56 UTCEPSS rescore
  4. 2026-08-16 11:54 UTCEG score recompute
  5. 2026-08-16 02:14 UTCEPSS rescore
  6. 2026-08-15 01:30 UTCEPSS rescore
  7. 2026-08-14 07:51 UTCEG score recompute
  8. 2026-08-13 22:00 UTCEPSS rescore
  9. 2026-08-12 23:02 UTCEG score recompute
  10. 2026-08-12 13:50 UTCEPSS rescore
  11. 2026-08-11 21:52 UTCEG score recompute
  12. 2026-08-11 13:42 UTCEPSS rescore
  13. 2026-08-11 04:59 UTCEG score recompute
  14. 2026-08-11 00:00 UTCEPSS rescore
  15. 2026-08-09 18:23 UTCEG score recompute
  16. 2026-08-09 13:46 UTCEPSS rescore
  17. 2026-08-09 07:32 UTCEG score recompute
  18. 2026-08-08 16:37 UTCEPSS rescore
  19. 2026-08-07 18:19 UTCEG score recompute
  20. 2026-08-06 19:55 UTCEG score recompute
  21. 2026-08-06 13:46 UTCEPSS rescore
  22. 2026-08-06 02:04 UTCEG score recompute
  23. 2026-08-05 19:17 UTCEPSS rescore
  24. 2026-08-04 15:10 UTCEPSS rescore
  25. 2026-08-04 10:38 UTCEPSS rescore
  26. 2026-08-04 01:22 UTCEG score recompute
  27. 2026-08-03 10:35 UTCEPSS rescore
  28. 2026-08-02 17:37 UTCEG score recompute
  29. 2026-08-02 02:26 UTCEPSS rescore
  30. 2026-08-01 04:15 UTCEPSS rescore
  31. 2026-07-30 01:30 UTCEPSS rescore
  32. 2026-07-27 14:13 UTCEPSS rescore
  33. 2026-07-27 13:43 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-21888?
CVE-2026-21888 is a high vulnerability published on March 11, 2026. NanoMQ MQTT Broker (NanoMQ) is an all-around Edge Messaging Platform. MQTT v5 Variable Byte Integer parsing out-of-bounds: getvarinteger() accepts 5-byte varints without bounds checks; reliably triggers OOB read / crash when built with ASan. This affects 0.24.6 and earlier.
When was CVE-2026-21888 disclosed?
CVE-2026-21888 was first published in the National Vulnerability Database on March 11, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-21888 actively exploited?
CVE-2026-21888 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 76.9% of all scored CVEs.
What is the CVSS score of CVE-2026-21888?
CVE-2026-21888 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-21888?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-21888, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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