CVE-2026-5857

HIGHPre-NVD 8.18.1—
EchelonGraph scoreMEDIUM confidence

Score 8.1 from GitHub Security Advisory (severity: CRITICAL) published 2026-08-07. A secondary CVSS source baseline 8.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
8.1EG
EchelonGraph verdictPlan mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.9%CVSS: 8.1Exploit: None knownExposed services: Not assessed

An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.

Contiki-NG's MQTT client parse_publish_vhdr() in os/net/app-layer/mqtt/mqtt.c sets topic_len_received=1 before checking topic_len against the 64-byte limit, so an over-length topic returns early but leaves the flag set. On the next TCP segment, tcp_input() re-invokes the parser with topic_received==0, and the persisted topic_len_received==1 skips the length-reading block containing the guard, falling through directly to a memcpy() that uses the unvalidated 16-bit topic_len as the copy length. The 65-byte topic[] destination overruns into adjacent struct fields including the payload_chunk pointer, which subsequent MQTT code dereferences, giving a compromised or attacker-controlled broker an arbitrary-pointer-write primitive. Contiki-NG's MQTT implementation has no TLS support so the connection is plaintext. Impact ranges from information disclosure and denial of service to remote code execution on embedded targets without memory protection.

CVSS v3
8.1
EG Score
8.1HIGHmedium confidence
EG Risk
52
EG Risk 52/100CISA SSVC

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
Severity81% × 45%
Exploitation1% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release.
EPSS PROB
0.9%
EPSS %ILE
58th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 6, 2026

Last Modified

September 24, 2026

Advisory Details (3)

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

commit a34a2dbdc8be (contiki-ng/contiki-ng)

Fix landed in contiki-ng/contiki-ng commit a34a2dbdc8be — awaiting tagged release

https://github.com/contiki-ng/contiki-ng/commit/a34a2dbdc8bea784bd2ae5079aa4be520cd74f2d
github_pr

mqtt: harden TCP input parsing against malformed and coalesced packets

Fix merged in contiki-ng/contiki-ng PR #3163 on 2026-07-10 — awaiting tagged release

https://github.com/contiki-ng/contiki-ng/pull/3163
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-2026-5857(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 17× in last 7d / 89× 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.

Showing the most recent 100 of 210 total refreshes for this CVE.

  1. 2026-10-04 23:22 UTCEPSS rescore
  2. 2026-10-04 23:22 UTCGHSA enrichment
  3. 2026-10-04 05:48 UTCEG score recompute
  4. 2026-10-04 05:48 UTCGHSA enrichment
  5. 2026-10-03 14:26 UTCEPSS rescore
  6. 2026-10-03 01:03 UTCEG score recompute
  7. 2026-10-03 01:03 UTCGHSA enrichment
  8. 2026-10-02 17:56 UTCEPSS rescore
  9. 2026-10-02 09:38 UTCEG score recompute
  10. 2026-10-02 09:38 UTCGHSA enrichment
  11. 2026-10-01 19:50 UTCEPSS rescore
  12. 2026-10-01 10:55 UTCGHSA enrichment
  13. 2026-09-30 23:01 UTCEG score recompute
  14. 2026-09-30 23:01 UTCGHSA enrichment
  15. 2026-09-30 15:03 UTCEPSS rescore
  16. 2026-09-29 05:53 UTCEG score recompute
  17. 2026-09-29 05:53 UTCGHSA enrichment
  18. 2026-09-28 13:51 UTCEPSS rescore
  19. 2026-09-28 05:00 UTCGHSA enrichment
  20. 2026-09-27 17:28 UTCEG score recompute
  21. 2026-09-27 17:28 UTCGHSA enrichment
  22. 2026-09-26 15:59 UTCEPSS rescore
  23. 2026-09-25 07:54 UTCGHSA enrichment
  24. 2026-09-24 20:17 UTCEG score recompute
  25. 2026-09-24 20:17 UTCGHSA enrichment
Show 75 more
  1. 2026-09-24 11:11 UTCGHSA enrichment
  2. 2026-09-23 23:39 UTCEG score recompute
  3. 2026-09-23 23:39 UTCGHSA enrichment
  4. 2026-09-23 17:54 UTCEPSS rescore
  5. 2026-09-23 11:56 UTCGHSA enrichment
  6. 2026-09-23 00:24 UTCEG score recompute
  7. 2026-09-23 00:24 UTCGHSA enrichment
  8. 2026-09-22 12:52 UTCGHSA enrichment
  9. 2026-09-22 01:01 UTCEG score recompute
  10. 2026-09-22 01:01 UTCGHSA enrichment
  11. 2026-09-21 12:46 UTCGHSA enrichment
  12. 2026-09-20 20:35 UTCEG score recompute
  13. 2026-09-20 20:35 UTCGHSA enrichment
  14. 2026-09-20 20:16 UTCEPSS rescore
  15. 2026-09-20 02:23 UTCEG score recompute
  16. 2026-09-20 02:23 UTCGHSA enrichment
  17. 2026-09-19 14:51 UTCGHSA enrichment
  18. 2026-09-19 03:10 UTCEG score recompute
  19. 2026-09-19 03:10 UTCGHSA enrichment
  20. 2026-09-18 19:28 UTCEPSS rescore
  21. 2026-09-18 14:44 UTCGHSA enrichment
  22. 2026-09-18 02:46 UTCEG score recompute
  23. 2026-09-18 02:46 UTCGHSA enrichment
  24. 2026-09-17 19:31 UTCEPSS rescore
  25. 2026-09-17 15:14 UTCGHSA enrichment
  26. 2026-09-17 00:57 UTCEG score recompute
  27. 2026-09-17 00:57 UTCGHSA enrichment
  28. 2026-09-16 14:08 UTCEPSS rescore
  29. 2026-09-16 05:15 UTCEPSS rescore
  30. 2026-09-16 02:58 UTCGHSA enrichment
  31. 2026-09-15 14:24 UTCEG score recompute
  32. 2026-09-15 14:24 UTCGHSA enrichment
  33. 2026-09-15 03:11 UTCEPSS rescore
  34. 2026-09-15 02:41 UTCGHSA enrichment
  35. 2026-09-14 14:56 UTCGHSA enrichment
  36. 2026-09-14 03:24 UTCEG score recompute
  37. 2026-09-14 03:24 UTCGHSA enrichment
  38. 2026-09-13 16:47 UTCEPSS rescore
  39. 2026-09-13 15:52 UTCGHSA enrichment
  40. 2026-09-13 04:20 UTCGHSA enrichment
  41. 2026-09-12 16:48 UTCEG score recompute
  42. 2026-09-12 16:48 UTCGHSA enrichment
  43. 2026-09-12 05:16 UTCGHSA enrichment
  44. 2026-09-11 17:44 UTCEG score recompute
  45. 2026-09-11 17:44 UTCGHSA enrichment
  46. 2026-09-11 14:53 UTCEPSS rescore
  47. 2026-09-11 05:51 UTCGHSA enrichment
  48. 2026-09-10 18:05 UTCEG score recompute
  49. 2026-09-10 18:05 UTCGHSA enrichment
  50. 2026-09-10 09:35 UTCEPSS rescore
  51. 2026-09-10 06:33 UTCGHSA enrichment
  52. 2026-09-09 18:51 UTCGHSA enrichment
  53. 2026-09-09 06:06 UTCEG score recompute
  54. 2026-09-09 06:06 UTCGHSA enrichment
  55. 2026-09-08 22:01 UTCEPSS rescore
  56. 2026-09-08 07:36 UTCGHSA enrichment
  57. 2026-09-07 17:52 UTCEG score recompute
  58. 2026-09-07 17:52 UTCGHSA enrichment
  59. 2026-09-07 16:01 UTCEPSS rescore
  60. 2026-09-06 15:34 UTCEG score recompute
  61. 2026-09-06 15:34 UTCGHSA enrichment
  62. 2026-09-06 13:47 UTCEPSS rescore
  63. 2026-09-06 03:52 UTCEG score recompute
  64. 2026-09-06 03:52 UTCGHSA enrichment
  65. 2026-09-05 16:21 UTCEG score recompute
  66. 2026-09-05 16:20 UTCGHSA enrichment
  67. 2026-09-05 03:30 UTCEG score recompute
  68. 2026-09-05 03:29 UTCGHSA enrichment
  69. 2026-09-04 09:11 UTCEG score recompute
  70. 2026-09-04 09:11 UTCGHSA enrichment
  71. 2026-09-04 05:07 UTCEPSS rescore
  72. 2026-09-03 17:49 UTCGHSA enrichment
  73. 2026-09-03 06:12 UTCEG score recompute
  74. 2026-09-03 06:12 UTCGHSA enrichment
  75. 2026-09-02 14:12 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-5857?
CVE-2026-5857 is a high vulnerability published on August 6, 2026. Contiki-NG's MQTT client parsepublishvhdr() in os/net/app-layer/mqtt/mqtt.c sets topiclenreceived=1 before checking topiclen against the 64-byte limit, so an over-length topic returns early but leaves the flag set. On the next TCP segment, tcpinput() re-invokes the parser with topicreceived==0, and…
When was CVE-2026-5857 disclosed?
CVE-2026-5857 was first published on August 6, 2026, with the most recent update on September 24, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-5857 actively exploited?
CVE-2026-5857 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.9% probability of exploitation in the next 30 days (58th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-5857?
CVE-2026-5857 has a CVSS base score of 8.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-5857?
An upstream fix for CVE-2026-5857 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-5857 are linked in the Vendor Advisories panel on this page.

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