# CVE-2026-127090: Jadaptive Maverick Synergy Server before 3.0.33 and 3.1.x before 3.1.7, and Maverick Legacy Server before 1.8.1, SSH Public Key Cross-User Authentication Bypass

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

Jadaptive Maverick Synergy Server before 3.0.33 and 3.1.x before 3.1.7, and Maverick Legacy Server before 1.8.1, contain an authentication bypass vulnerability in SSH public key authentication that reuses cached key authorization decisions across usernames. Attackers holding a key authorized for one account can authenticate it, then send a signed SSH_MSG_USERAUTH_REQUEST with a different username on the same connection to log in as that account.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/sshtools/maverick-synergy/commit/f7d23182cce985e21048215e96395881295cb0bd

## Affected products and versions

- Jadaptive / Maverick Synergy Server (com.sshtools/maverick-synergy-server): ≥ 0; < 3.0.33 (affected, semver); ≥ 3.1.0; < 3.1.7 (affected, semver). Source: CNA: VulnCheck
- Jadaptive / Maverick Legacy Server: ≥ 0; < 1.8.1 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.7 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.76% as of 2026-11-13; percentile 55.86%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-305

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://jadaptive.com/security/advisories/JADAPTIVE-SA-2026-001 (CNA: VulnCheck; vendor-advisory)

- https://github.com/sshtools/maverick-synergy/commit/f7d23182cce985e21048215e96395881295cb0bd (CNA: VulnCheck; patch)

- https://store.jadaptive.com/app/api/releases/changes/01d04a39-0f05-4bae-842e-d2f1acc16985 (CNA: VulnCheck; release-notes)

- https://store.jadaptive.com/app/api/releases/changes/ff71bdcf-a2a2-47e0-af5a-22e15af1dfa4 (CNA: VulnCheck; release-notes)

- https://github.com/sshtools/maverick-synergy/blob/3.1.4/maverick-base/src/main/java/com/sshtools/common/auth/PublicKeyAuthentication.java#L82-L100 (CNA: VulnCheck; technical-description)

- https://github.com/sshtools/maverick-synergy/blob/3.1.4/maverick-synergy-server/src/main/java/com/sshtools/server/AuthenticationProtocolServer.java#L185-L200 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/jadaptive-maverick-synergy-server-before-3.0.33-and-3.1-x-before-3.1.7-and-maverick-legacy-server-before-1.8.1-ssh-public-key-cross-user-authentication-bypass (CNA: VulnCheck; third-party-advisory)

- https://github.com/sshtools/maverick-synergy/blob/3.1.4/maverick-base/src/main/java/com/sshtools/common/auth/PublicKeyAuthentication.java#L82-L100 (disclosure@vulncheck.com)

- https://github.com/sshtools/maverick-synergy/blob/3.1.4/maverick-synergy-server/src/main/java/com/sshtools/server/AuthenticationProtocolServer.java#L185-L200 (disclosure@vulncheck.com)

- https://github.com/sshtools/maverick-synergy/commit/f7d23182cce985e21048215e96395881295cb0bd (disclosure@vulncheck.com)

- https://jadaptive.com/security/advisories/JADAPTIVE-SA-2026-001 (disclosure@vulncheck.com)

- https://store.jadaptive.com/app/api/releases/changes/01d04a39-0f05-4bae-842e-d2f1acc16985 (disclosure@vulncheck.com)

- https://store.jadaptive.com/app/api/releases/changes/ff71bdcf-a2a2-47e0-af5a-22e15af1dfa4 (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/jadaptive-maverick-synergy-server-before-3.0.33-and-3.1-x-before-3.1.7-and-maverick-legacy-server-before-1.8.1-ssh-public-key-cross-user-authentication-bypass (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-127090; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-127090; retrieved 2026-11-13; source updated 2026-11-13

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-127090; retrieved 2026-11-13; source updated Not reported

Revision: efc47e6572be3686a569eb2859d92739d2360dc139e5333938fd7dff7958c1c7

Canonical: https://y2.dev/cve/CVE-2026-127090

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