CVE-2026-3706mkj Dropbear S Range Check curve25519.c unpackneg signature verification
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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."
- CVSS
- 3.7 LOW (v3.1, CNA)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
- Weakness (CWE)
- CWE-347, CWE-345
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulDB
- NVD analysis
- Deferred
- Record last updated
- Apr 22, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
mkj Dropbear mkj:dropbear (from the name) | 2025.0; 2025.1; 2025.2; 2025.3; 2025.4; 2025.5; 2025.6; 2025.7; and 82 more ranges | CNA record |
References
- https://vuldb.com/?id.349652vdb-entry, technical-description
- https://vuldb.com/?ctiid.349652signature, permissions-required
- https://vuldb.com/?submit.765933third-party-advisory
- https://github.com/mkj/dropbear/issues/406issue-tracking
- https://github.com/mkj/dropbear/pull/407issue-tracking, patch
- https://github.com/mkj/dropbear/commit/fdec3c90a15447bd538641d85e5a3e3ac981011dpatch
- https://github.com/str4d/ed25519-java/issues/82#issue-727629226issue-tracking
- https://github.com/mkj/dropbear/product
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.