CVE-2026-55606

MEDIUMPre-NVD 6.56.5
EchelonGraph scoreMEDIUM confidence

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

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (40th 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
Elevated

Also known asEUVD-2026-108970 (ENISA EUVD)Source: ENISA EUVD

6.5EG
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).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 6.5Exploit: No code on recordExposed services: Not assessed

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

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In versions 25.12 and prior, odhcpd's DHCPv6 self-loop detection at dhcpv6.c:720 uses a network-byte-order DUID length value directly as the memcmp() size parameter. On little-endian hosts, this causes memcmp() to read far beyond the stack buffer — a single unauthenticated DHCPv6 packet triggers a 2560-byte overread from a 128-byte buffer. At time of publication, there are no publicly available patches.

CVSS v3
6.5
EG Score
6.5MEDIUMmedium confidence
EG Risk
60
EG Risk 60/100

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)
Severity65% × 45%
Impact severity (EG Severity): CVSS 6.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
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 public PoC (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
0.5%
EPSS %ILE
40th
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 (6.5): severity, escalated by confirmed exploitation. This CVE's 6.5 is its impact severity (EG Severity), not escalated.

EG Severity
6.5 MEDIUMCVSS-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
0.5% within 30 daysSource: FIRST EPSS. 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 public PoC (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 23, 2026

Last Modified

October 29, 2026

Advisory Details (4)

Auto-updated Oct 23, 2026
🔬 Proof of concept available. No fix on record yet. Sources: github, github_pr, github_commit.
GitHub commit

commit ed38cffa927d (openwrt/odhcpd)

Fix landed in openwrt/odhcpd commit ed38cffa927d — awaiting tagged release

https://github.com/openwrt/odhcpd/commit/ed38cffa927d5fd450d20bfd3f7fb8d8e8fff301
GitHub commit

commit 6907f28f9dde (openwrt/odhcpd)

Fix landed in openwrt/odhcpd commit 6907f28f9dde — awaiting tagged release

https://github.com/openwrt/odhcpd/commit/6907f28f9ddeef9f69f5ee10bbc9ba8adc0ef57f
GitHub pull request

Harden DHCPv6/DHCPv4/NDP packet parsing against malformed input

Fix merged in openwrt/odhcpd PR #401 on 2026-06-03 — awaiting tagged release

https://github.com/openwrt/odhcpd/pull/401
GitHub advisoryMentions a patch (unverified)🟡 PoC Available

Stack buffer overread via DUID length endianness mismatch in memcmp() · Advisory · openwrt/odhcpd · GitHub

https://github.com/openwrt/odhcpd/security/advisories/GHSA-x8x4-7gvf-gp45

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 15× 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. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  3. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  4. 2026-10-29 18:27 UTCEG score recompute
  5. 2026-10-29 17:54 UTCEG score recompute
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  9. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 31st percentile
  11. 2026-10-25 14:18 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 40th percentile
  13. 2026-10-23 14:28 UTCEG score recompute
  14. 2026-10-23 13:27 UTCEG score recomputeFirst assessed: 6.5 MEDIUM
  15. 2026-10-23 13:24 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-55606?
CVE-2026-55606 is a medium-severity vulnerability; its CVE record was published on October 23, 2026. odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In versions 25.12 and prior, odhcpd's DHCPv6 self-loop detection at dhcpv6.c:720 uses a network-byte-order DUID length value directly as the memcmp() size parameter. On little-endian hosts, this causes memcmp() to read…
When was the CVE record for CVE-2026-55606 published?
The CVE record for CVE-2026-55606 was published on October 23, 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 29, 2026; the record at its source may have been updated since.
Is CVE-2026-55606 actively exploited?
CVE-2026-55606 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (40th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55606?
CVE-2026-55606 has a CVSS base score of 6.5 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55606?
No fix for CVE-2026-55606 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.

Dependency Blast Radius

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