CVE-2026-3706 (GCVE-0-2026-3706)
Vulnerability from cvelistv5 – Published: 2026-03-08 05:02 – Updated: 2026-04-22 18:54 Disputed X_Open Source
VLAI
EPSS
VEX
Title
mkj Dropbear S Range Check curve25519.c unpackneg signature verification
Summary
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."
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-10 14:05 UTC
CWE
Assigner
References
8 references
| URL | Tags |
|---|---|
| https://vuldb.com/?id.349652 | vdb-entrytechnical-description |
| https://vuldb.com/?ctiid.349652 | signaturepermissions-required |
| https://vuldb.com/?submit.765933 | third-party-advisory |
| https://github.com/mkj/dropbear/issues/406 | issue-tracking |
| https://github.com/mkj/dropbear/pull/407 | issue-trackingpatch |
| https://github.com/mkj/dropbear/commit/fdec3c90a1… | patch |
| https://github.com/str4d/ed25519-java/issues/82#i… | issue-tracking |
| https://github.com/mkj/dropbear/ | product |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| mkj | Dropbear |
Affected:
2025.0
Affected: 2025.1 Affected: 2025.2 Affected: 2025.3 Affected: 2025.4 Affected: 2025.5 Affected: 2025.6 Affected: 2025.7 Affected: 2025.8 Affected: 2025.9 Affected: 2025.10 Affected: 2025.11 Affected: 2025.12 Affected: 2025.13 Affected: 2025.14 Affected: 2025.15 Affected: 2025.16 Affected: 2025.17 Affected: 2025.18 Affected: 2025.19 Affected: 2025.20 Affected: 2025.21 Affected: 2025.22 Affected: 2025.23 Affected: 2025.24 Affected: 2025.25 Affected: 2025.26 Affected: 2025.27 Affected: 2025.28 Affected: 2025.29 Affected: 2025.30 Affected: 2025.31 Affected: 2025.32 Affected: 2025.33 Affected: 2025.34 Affected: 2025.35 Affected: 2025.36 Affected: 2025.37 Affected: 2025.38 Affected: 2025.39 Affected: 2025.40 Affected: 2025.41 Affected: 2025.42 Affected: 2025.43 Affected: 2025.44 Affected: 2025.45 Affected: 2025.46 Affected: 2025.47 Affected: 2025.48 Affected: 2025.49 Affected: 2025.50 Affected: 2025.51 Affected: 2025.52 Affected: 2025.53 Affected: 2025.54 Affected: 2025.55 Affected: 2025.56 Affected: 2025.57 Affected: 2025.58 Affected: 2025.59 Affected: 2025.60 Affected: 2025.61 Affected: 2025.62 Affected: 2025.63 Affected: 2025.64 Affected: 2025.65 Affected: 2025.66 Affected: 2025.67 Affected: 2025.68 Affected: 2025.69 Affected: 2025.70 Affected: 2025.71 Affected: 2025.72 Affected: 2025.73 Affected: 2025.74 Affected: 2025.75 Affected: 2025.76 Affected: 2025.77 Affected: 2025.78 Affected: 2025.79 Affected: 2025.80 Affected: 2025.81 Affected: 2025.82 Affected: 2025.83 Affected: 2025.84 Affected: 2025.85 Affected: 2025.86 Affected: 2025.87 Affected: 2025.88 Affected: 2025.89 |
guessed |
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"value": "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\u0027t exist for SSH implementation, but rather it\u0027s against the internal API.\""
},
{
"lang": "es",
"value": "Se determin\u00f3 una vulnerabilidad en mkj Dropbear hasta 2025.89. La funci\u00f3n unpackneg del archivo src/curve25519.c del componente S Range Check se ve afectada. Esta manipulaci\u00f3n provoca una verificaci\u00f3n incorrecta de la firma criptogr\u00e1fica. El ataque puede iniciarse de forma remota. Se considera que el ataque tiene una complejidad alta. La explotabilidad se considera dif\u00edcil. El exploit ha sido divulgado p\u00fablicamente y puede ser utilizado. Nombre del parche: fdec3c90a15447bd538641d85e5a3e3ac981011d. Para solucionar este problema, se recomienda desplegar un parche."
}
],
"id": "CVE-2026-3706",
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},
"redhat_vex": {
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"source": "Red Hat CSAF VEX",
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"title": "mkj Dropbear S Range Check curve25519.c unpackneg signature verification",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-3706.json",
"version": "3"
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],
"url": "https://github.com/mkj/dropbear/issues/406"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
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{
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],
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],
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],
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"value": "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\u0027t exist for SSH implementation, but rather it\u0027s against the internal API.\""
}
],
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}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.