CVE Intelligence
Low Integrity

CVE-2026-3706 — mkj Dropbear S Range Check curve25519.c unpackneg signature verification

A vulnerability was determined in mkj Dropbear up to 2025.89. Impacted is the function unpackneg of the file src/curve25519.c of the component S Range Check. This manipulation causes improper verification of cryptographic signature. The attack can be initiated remotely. The attack is considered to have high complexity. The exploitability is considered difficult. The actual existence of this vulnerability is currently in question. Patch name: fdec3c90a15447bd538641d85e5a3e3ac981011d. To fix this issue, it is recommended to deploy a patch. The project maintainer explains: "Signature Malleability is not exploitable in SSH protocol. (...) [A] PoC doesn't exist for SSH implementation, but rather it's against the internal API."

Published Mar 8, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: VulDB

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.2% (30-day exploitation probability)+1
  • CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.19%
ahead of 8% of scored CVEs · Oct 14, 2026
Affects
Mkj
Dropbear
CVSS base
3.7
Low · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Proof of concept
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Mkj Dropbear).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  4. Search available logs for exploit probes matching the vulnerability class (integrity), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Mkj Dropbear version 2025.56version 2025.67version 2025.66version 2025.65version 2025.64version 2025.63version 2025.62version 2025.61
and 82 more version 2025.60version 2025.59version 2025.58version 2025.57version 2025.68version 2025.55version 2025.54version 2025.53version 2025.52version 2025.51version 2025.50version 2025.49version 2025.48version 2025.47version 2025.46version 2025.79version 2025.89version 2025.88version 2025.87version 2025.86version 2025.85version 2025.84version 2025.83version 2025.82version 2025.81version 2025.80version 2025.45version 2025.78version 2025.77version 2025.76version 2025.75version 2025.74version 2025.73version 2025.72version 2025.71version 2025.70version 2025.69version 2025.11version 2025.22version 2025.21version 2025.20version 2025.19version 2025.18version 2025.17version 2025.16version 2025.15version 2025.14version 2025.13version 2025.12version 2025.23version 2025.10version 2025.9version 2025.8version 2025.7version 2025.6version 2025.5version 2025.4version 2025.3version 2025.2version 2025.1version 2025.34version 2025.44version 2025.43version 2025.42version 2025.41version 2025.40version 2025.39version 2025.38version 2025.37version 2025.36version 2025.35version 2025.0version 2025.33version 2025.32version 2025.31version 2025.30version 2025.29version 2025.28version 2025.27version 2025.26version 2025.25version 2025.24
Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.3 CVSS 4.0 Medium — — VulDB via CVE Program (cve.org) e CISA ADP
1.7 CVSS 4.0 Low — — cna@vuldb.com via NIST National Vulnerability Database
3.7 CVSS 3.1 Low 2.2 1.4 cna@vuldb.com via NIST National Vulnerability Database
3.7 CVSS 3.1 Low — — VulDB via CVE Program (cve.org) e CISA ADP
3.7 CVSS 3.0 Low — — VulDB via CVE Program (cve.org) e CISA ADP
2.6 CVSS 2.0 Low 4.9 2.9 cna@vuldb.com via NIST National Vulnerability Database
2.6 CVSS 2.0 Low — — VulDB via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N (score shown at the top: cna@vuldb.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-345 · Insufficient Verification of Data Authenticity

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.19%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · mkj/dropbear
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • CVSS changed · 3.7
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Deferred
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Mar 8, 2026 · VulDB

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

8 on the record

Elsewhere on this site

Mkj
every CVE for this vendor
Integrity
same class
CWE-345
other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-3706 is "mkj Dropbear S Range Check curve25519.c unpackneg signature verification", rated Low. It affects Dropbear (Mkj); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 3.7 describes technical severity. EPSS 0.19% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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