CVE-2026-107838

HIGHPre-NVD 7.57.5
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (27th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source

Also known asEUVD-2026-95933 (ENISA EUVD)Source: ENISA EUVD

7.5EG
EchelonGraph verdictPlan mitigationNo fix is confirmed yet: check with the vendor for a fixed release; until one is applied, restrict network exposure of the affected system on your normal schedule at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 7.5Exploit: None knownExposed services: Not assessed

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

The CVE record's description, written by its CNA (GitHub, Inc.), states the affected versions: "From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/fileserver.c ignore a failure returned by _resp_init() when coap_build_reply() cannot fit a response header…" No release containing a fix is confirmed on record.

RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/fileserver.c ignore a failure returned by _resp_init() when coap_build_reply() cannot fit a response header into the response buffer. A remote client can send a CoAP request with a sufficiently large extended token when nanocoap_token_ext is enabled, causing response initialization to fail while _get_file() or _get_directory() continues with stale response state. The path then reaches _calc_szx2() and its pdu->payload_len > reserve assertion, terminating the affected service or device task. No fixed release is available as of this review.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: No fix is confirmed yet. Check with the vendor for a fixed release; until one is applied, restrict network exposure of the affected system on your normal schedule at low or medium mission impact and sooner than that at high.
EPSS PROB
0.3%
EPSS %ILE
27th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

No fix is confirmed yet. Check with the vendor for a fixed release; until one is applied, restrict network exposure of the affected system on your normal schedule at low or medium mission impact and sooner than that at high.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

October 9, 2026

Last Modified

October 16, 2026

Advisory Details (3)

Auto-updated Oct 9, 2026
No fix on record yet. Sources: github_commit, github, github_pr.
GitHub commit

commit d3a47289c58d (RIOT-OS/RIOT)

Fix landed in RIOT-OS/RIOT commit d3a47289c58d — awaiting tagged release

https://github.com/RIOT-OS/RIOT/commit/d3a47289c58d108575a19e623e4d3f647659e743
GitHub pull request

sys/net/nanocoap_fileserver: always check return value of _resp_init()

Fix merged in RIOT-OS/RIOT PR #22745 on 2026-09-21 — awaiting tagged release

https://github.com/RIOT-OS/RIOT/pull/22745
GitHub advisoryMentions a patch (unverified)

nanocoap_fileserver ignores response initialization failure, leading to reachable assertion · Advisory · RIOT-OS/RIOT · GitHub

https://github.com/RIOT-OS/RIOT/security/advisories/GHSA-39j3-3v73-5mj2

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 38× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  2. 2026-11-01 01:22 UTCEG score recompute
  3. 2026-10-31 16:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  4. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  5. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  6. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  7. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  8. 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  9. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  10. 2026-10-25 14:54 UTCEG score recompute
  11. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  12. 2026-10-24 09:26 UTCEG score recompute
  13. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  14. 2026-10-22 16:33 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  15. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  16. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  17. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  18. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  19. 2026-10-18 05:07 UTCEG score recompute
  20. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  21. 2026-10-16 17:28 UTCEG score recompute
  22. 2026-10-16 16:40 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  23. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  24. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  25. 2026-10-13 18:26 UTCEG score recompute
Show 13 more
  1. 2026-10-13 17:20 UTCEG score recompute
  2. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  3. 2026-10-12 16:38 UTCEG score recompute
  4. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  5. 2026-10-11 20:14 UTCEG score recompute
  6. 2026-10-11 16:34 UTCEG score recompute
  7. 2026-10-11 15:00 UTCEG score recompute
  8. 2026-10-11 13:47 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  9. 2026-10-11 05:01 UTCEG score recompute
  10. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.3% · 25th percentile
  11. 2026-10-09 18:34 UTCEG score recompute
  12. 2026-10-09 18:03 UTCEG score recomputeFirst assessed: 7.5 HIGH
  13. 2026-10-09 18:03 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-107838?
CVE-2026-107838 is a high-severity vulnerability; its CVE record was published on October 9, 2026. RIOT is an open-source microcontroller operating system designed for Internet of Things devices and other embedded systems. From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/fileserver.c ignore a failure returned by _resp_init() when…
When was the CVE record for CVE-2026-107838 published?
The CVE record for CVE-2026-107838 was published on October 9, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 16, 2026; the record at its source may have been updated since.
Is CVE-2026-107838 actively exploited?
CVE-2026-107838 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (27th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-107838?
CVE-2026-107838 has a CVSS base score of 7.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-107838?
No fix for CVE-2026-107838 is confirmed yet. Until one is published, restrict network exposure of the affected system — for example, keep it off the internet or limit it to trusted networks — and watch for a fix. The CVE record's description, written by its CNA (GitHub, Inc.), states the affected versions: "From version 2023.07 through version 2026.07, nanocoap_fileserver callers in sys/net/application_layer/nanocoap/fileserver.c ignore a failure returned by _resp_init() when coap_build_reply() cannot fit a response header…" No release containing a fix is confirmed on record.

Dependency Blast Radius

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