{"id":"UBUNTU-CVE-2026-3706","details":"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.\"","modified":"2026-09-16T14:01:34.198982823Z","published":"2026-03-08T05:16:00Z","upstream":["CVE-2026-3706"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-3706"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-3706"},{"type":"REPORT","url":"https://github.com/mkj/dropbear/issues/406"},{"type":"REPORT","url":"https://github.com/mkj/dropbear/pull/407"},{"type":"REPORT","url":"https://github.com/mkj/dropbear/"},{"type":"REPORT","url":"https://github.com/mkj/dropbear/commit/fdec3c90a15447bd538641d85e5a3e3ac981011d"},{"type":"REPORT","url":"https://github.com/mkj/dropbear/issues/406#issue-3978907798"},{"type":"REPORT","url":"https://github.com/str4d/ed25519-java/issues/82#issue-727629226"},{"type":"REPORT","url":"https://vuldb.com/?ctiid.349652"},{"type":"REPORT","url":"https://vuldb.com/?id.349652"},{"type":"REPORT","url":"https://vuldb.com/?submit.765933"}],"affected":[{"package":{"name":"dropbear","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2014.65-1ubuntu2","2015.68-1","2015.70-1","2015.71-1","2016.72-1"],"ecosystem_specific":{"binaries":[{"binary_version":"2016.72-1","binary_name":"dropbear"},{"binary_version":"2016.72-1","binary_name":"dropbear-bin"},{"binary_name":"dropbear-initramfs","binary_version":"2016.72-1"},{"binary_name":"dropbear-run","binary_version":"2016.72-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}},{"package":{"name":"dropbear","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2017.75-2","2017.75-3build1","2017.75-3ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"2017.75-3ubuntu0.1~esm1","binary_name":"dropbear"},{"binary_version":"2017.75-3ubuntu0.1~esm1","binary_name":"dropbear-bin"},{"binary_version":"2017.75-3ubuntu0.1~esm1","binary_name":"dropbear-initramfs"},{"binary_version":"2017.75-3ubuntu0.1~esm1","binary_name":"dropbear-run"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}},{"package":{"name":"dropbear","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=esm-apps%2Ffocal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2019.78-2build1","2019.78-2ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"2019.78-2ubuntu0.1~esm1","binary_name":"dropbear"},{"binary_version":"2019.78-2ubuntu0.1~esm1","binary_name":"dropbear-bin"},{"binary_name":"dropbear-initramfs","binary_version":"2019.78-2ubuntu0.1~esm1"},{"binary_name":"dropbear-run","binary_version":"2019.78-2ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}},{"package":{"name":"dropbear","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2020.81-3","2020.81-4","2020.81-5","2020.81-5ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_version":"2020.81-5ubuntu0.1","binary_name":"dropbear"},{"binary_name":"dropbear-bin","binary_version":"2020.81-5ubuntu0.1"},{"binary_name":"dropbear-initramfs","binary_version":"2020.81-5ubuntu0.1"},{"binary_name":"dropbear-run","binary_version":"2020.81-5ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}},{"package":{"name":"dropbear","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2022.83-2","2022.83-3","2022.83-4"],"ecosystem_specific":{"binaries":[{"binary_name":"dropbear","binary_version":"2022.83-4"},{"binary_version":"2022.83-4","binary_name":"dropbear-bin"},{"binary_name":"dropbear-initramfs","binary_version":"2022.83-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}},{"package":{"name":"dropbear","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2024.86-2","2025.88-2"],"ecosystem_specific":{"binaries":[{"binary_name":"dropbear","binary_version":"2025.88-2"},{"binary_name":"dropbear-bin","binary_version":"2025.88-2"},{"binary_name":"dropbear-initramfs","binary_version":"2025.88-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}},{"package":{"name":"dropbear","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/dropbear?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2025.88-2","2025.89-1"],"ecosystem_specific":{"binaries":[{"binary_name":"dropbear","binary_version":"2025.89-1"},{"binary_name":"dropbear-bin","binary_version":"2025.89-1"},{"binary_name":"dropbear-initramfs","binary_version":"2025.89-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-3706.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"},{"type":"CVSS_V4","score":"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":"Ubuntu","score":"medium"}]}