CVE-2026-5855

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-08-07. the CNA's CVSS baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cna:vulncheck, epss, ghsa
Trending — 3 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 0

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

Contiki-NG's LwM2M TLV parser lwm2m_tlv_read() in os/services/lwm2m/lwm2m-tlv.c ignores its caller-supplied buffer length argument and reads up to six bytes from the input buffer with no bounds check. The caller in lwm2m-engine.c iterates while there is at least one byte remaining, so a crafted CoAP WRITE to any LwM2M endpoint whose final TLV supplies exactly one byte triggers up to five out-of-bounds reads of heap memory adjacent to the CoAP input buffer, disclosing memory contents (including key material and peer addresses) through the parsed tlv->id, tlv->length, and tlv->value fields. Corrupted tlv_len derived from the out-of-bounds memory further corrupts the caller's parse offset. In LwM2M NoSec mode, the default for constrained devices, no authentication is required.

CVSS v3
7.5
EG Score
7.5(high)
EG Risk
49(Track)
EG Risk 49/100SSVC: 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%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

August 6, 2026

Last Modified

August 14, 2026

Advisory Details (3)

Auto-updated Aug 6, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr, github_commit.
github_pr

lwm2m-tlv: bounds-check lwm2m_tlv_read against available buffer length

Fix merged in contiki-ng/contiki-ng PR #3165 on 2026-07-08 — awaiting tagged release

https://github.com/contiki-ng/contiki-ng/pull/3165
github_commit

commit f1673b5766d4 (contiki-ng/contiki-ng)

Fix landed in contiki-ng/contiki-ng commit f1673b5766d4 — awaiting tagged release

https://github.com/contiki-ng/contiki-ng/commit/f1673b5766d4d4d514cefb8a0350f43653574997
generic

GitHub - contiki-ng/contiki-ng: Contiki-NG: The OS for Next Generation IoT Devices · GitHub

https://github.com/contiki-ng/contiki-ng

Vendor Advisories for CVE-2026-5855(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 29× in last 7d / 59× 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. 2026-08-20 10:14 UTCGHSA enrichment
  2. 2026-08-19 22:54 UTCEG score recompute
  3. 2026-08-19 22:54 UTCGHSA enrichment
  4. 2026-08-19 17:04 UTCEPSS rescore
  5. 2026-08-19 11:32 UTCGHSA enrichment
  6. 2026-08-19 00:10 UTCEG score recompute
  7. 2026-08-19 00:10 UTCGHSA enrichment
  8. 2026-08-18 13:48 UTCEPSS rescore
  9. 2026-08-18 12:48 UTCGHSA enrichment
  10. 2026-08-18 00:57 UTCEG score recompute
  11. 2026-08-18 00:57 UTCGHSA enrichment
  12. 2026-08-17 13:47 UTCEPSS rescore
  13. 2026-08-17 13:16 UTCGHSA enrichment
  14. 2026-08-17 01:56 UTCEG score recompute
  15. 2026-08-17 01:56 UTCGHSA enrichment
  16. 2026-08-16 14:56 UTCEPSS rescore
  17. 2026-08-16 14:35 UTCGHSA enrichment
  18. 2026-08-16 03:14 UTCEG score recompute
  19. 2026-08-16 03:14 UTCGHSA enrichment
  20. 2026-08-15 15:53 UTCGHSA enrichment
  21. 2026-08-15 04:32 UTCEG score recompute
  22. 2026-08-15 04:32 UTCGHSA enrichment
  23. 2026-08-15 01:30 UTCEPSS rescore
  24. 2026-08-14 17:10 UTCEG score recompute
  25. 2026-08-14 17:10 UTCGHSA enrichment
Show 34 more
  1. 2026-08-14 08:17 UTCEG score recompute
  2. 2026-08-14 08:17 UTCGHSA enrichment
  3. 2026-08-13 22:00 UTCEPSS rescore
  4. 2026-08-13 20:56 UTCGHSA enrichment
  5. 2026-08-13 09:35 UTCGHSA enrichment
  6. 2026-08-12 22:14 UTCEG score recompute
  7. 2026-08-12 22:14 UTCGHSA enrichment
  8. 2026-08-12 13:51 UTCEPSS rescore
  9. 2026-08-12 10:54 UTCGHSA enrichment
  10. 2026-08-11 23:33 UTCEG score recompute
  11. 2026-08-11 23:33 UTCGHSA enrichment
  12. 2026-08-11 12:12 UTCGHSA enrichment
  13. 2026-08-11 00:51 UTCEG score recompute
  14. 2026-08-11 00:51 UTCGHSA enrichment
  15. 2026-08-11 00:00 UTCEPSS rescore
  16. 2026-08-10 13:30 UTCGHSA enrichment
  17. 2026-08-10 02:09 UTCGHSA enrichment
  18. 2026-08-09 14:48 UTCEG score recompute
  19. 2026-08-09 14:48 UTCGHSA enrichment
  20. 2026-08-09 13:46 UTCEPSS rescore
  21. 2026-08-09 03:28 UTCEG score recompute
  22. 2026-08-09 03:28 UTCGHSA enrichment
  23. 2026-08-08 16:37 UTCEPSS rescore
  24. 2026-08-08 16:07 UTCGHSA enrichment
  25. 2026-08-08 04:46 UTCGHSA enrichment
  26. 2026-08-07 17:25 UTCEG score recompute
  27. 2026-08-07 17:25 UTCGHSA enrichment
  28. 2026-08-07 16:27 UTCEG score recompute
  29. 2026-08-07 16:27 UTCGHSA enrichment
  30. 2026-08-07 09:42 UTCEG score recompute
  31. 2026-08-07 09:42 UTCGHSA enrichment
  32. 2026-08-06 22:22 UTCEG score recompute
  33. 2026-08-06 22:16 UTCEG score recompute
  34. 2026-08-06 22:15 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-5855?
CVE-2026-5855 is a high vulnerability published on August 6, 2026. Contiki-NG's LwM2M TLV parser lwm2mtlvread() in os/services/lwm2m/lwm2m-tlv.c ignores its caller-supplied buffer length argument and reads up to six bytes from the input buffer with no bounds check. The caller in lwm2m-engine.c iterates while there is at least one byte remaining, so a crafted CoAP…
When was CVE-2026-5855 disclosed?
CVE-2026-5855 was first published in the National Vulnerability Database on August 6, 2026, with the most recent update on August 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-5855 actively exploited?
CVE-2026-5855 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 57.0% of all scored CVEs.
What is the CVSS score of CVE-2026-5855?
CVE-2026-5855 has a CVSS v4.0 base score of 7.5 (CNA self-assessment; NVD's own analysis pending).
How do I remediate CVE-2026-5855?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-5855, 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.

Dependency Blast Radius

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