CVE-2026-3706

mkj Dropbear S Range Check curve25519.c unpackneg signature verification

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Published Mar 8, 2026 CVSS 4.0 · 6.3 Medium EPSS < 1% KEV · Not listed
Description
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."

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
References
Type Values Removed Values Added
Description 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 exploit has been publicly disclosed and may be utilized. Patch name: fdec3c90a15447bd538641d85e5a3e3ac981011d. To fix this issue, it is recommended to deploy a patch. 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."
References
Metrics cvssV2_0

{'score': 2.6, 'vector': 'AV:N/AC:H/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C'}

cvssV3_0

{'score': 3.7, 'vector': 'CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C'}

cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P'}

 cvssV2_0

{'score': 2.6, 'vector': 'AV:N/AC:H/Au:N/C:N/I:P/A:N/E:U/RL:OF/RC:C'}

cvssV3_0

{'score': 3.7, 'vector': 'CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C'}

cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U'}
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}
Type Values Removed Values Added
First Time appeared Mkj
Mkj dropbear
Vendors & Products Mkj
Mkj dropbear
Type Values Removed Values Added
Description 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 exploit has been publicly disclosed and may be utilized. Patch name: fdec3c90a15447bd538641d85e5a3e3ac981011d. To fix this issue, it is recommended to deploy a patch.
Title mkj Dropbear S Range Check curve25519.c unpackneg signature verification
Weaknesses CWE-345
CWE-347
References
Metrics cvssV2_0

{'score': 2.6, 'vector': 'AV:N/AC:H/Au:N/C:N/I:P/A:N/E:POC/RL:OF/RC:C'}

cvssV3_0

{'score': 3.7, 'vector': 'CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C'}

cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P'}
Weaknesses

Sources

Status
PUBLISHED
Assigner
VulDB
Published
Updated
Apr 22, 2026, 6:54 PM
Reserved
Mar 7, 2026, 9:05 AM

View source JSON

Updated
Mar 10, 2026, 2:06 PM

JSON

Status
Deferred
Published
Mar 8, 2026, 5:16 AM
Modified
Jun 17, 2026, 10:44 AM

View source JSON

No data.

Updated
Apr 16, 2026, 10:45 AM

JSON