Security advisories - Synergy

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A standard user can stop an administrator's locked settings being enforced

medium

Identifier: GHSA-2vgw-p6fp-mg7w
Affected versions: Synergy 1: >= 1.21.2, < 1.22.3
Synergy 3: >= 3.8.0-beta, < 3.8.4
Fixed in: Synergy 1: 1.22.3
Synergy 3: 3.8.4
CVSS: 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N)

Odd-length DSOP options vector causes out-of-bounds read in the client

high

Identifier: CVE-2026-63409
Affected versions: Synergy 1: < 1.21.2
Synergy 3: < 3.7.1
Fixed in: Synergy 1: 1.21.2
Synergy 3: 3.7.1
CVSS: 8.2 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H)

Unauthenticated server-controlled out-of-bounds read in modifier-table indexing

high

Identifier: CVE-2026-65832
Affected versions: Synergy 1: < 1.21.2
Synergy 3: < 3.7.1
Fixed in: Synergy 1: 1.21.2
Synergy 3: 3.7.1
CVSS: 8.2 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H)

Single-byte LSYN language payload causes uncaught exception in client

high

Identifier: GHSA-hcw4-4hv9-mmrf
Affected versions: Synergy 1: < 1.21.2
Synergy 3: < 3.7.1
Synergy Dragon: < 0.5.0
Fixed in: Synergy 1: 1.21.2
Synergy 3: 3.7.1
Synergy Dragon: 0.5.0
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Clipboard receiver can accumulate data beyond the configured clipboard size limit

medium

Identifier: CVE-2026-65976
Affected versions: Synergy 1: < 1.21.2
Synergy 3: < 3.7.1
Fixed in: Synergy 1: 1.21.2
Synergy 3: 3.7.1
CVSS: 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H)

Does not sufficiently verify the identity of connecting clients

high

Identifier: CVE-2021-42072
Affected versions: Synergy 1: < 1.21.0-beta
Synergy 3: < 3.7.1
Synergy Dragon: < 0.6.0
Fixed in: Synergy 1: 1.21.0-beta
Synergy 3: 3.7.1
Synergy Dragon: 0.6.0
CVSS: 8.8 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

Attacker can enter an active session state

high

Identifier: CVE-2021-42073
Affected versions: Synergy 1: < 1.21.0-beta
Synergy 3: < 3.7.1
Synergy Dragon: < 0.6.0
Fixed in: Synergy 1: 1.21.0-beta
Synergy 3: 3.7.1
Synergy Dragon: 0.6.0
CVSS: 8.2 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N)

Attacker can cause a segmentation fault in the server component

high

Identifier: CVE-2021-42074
Affected versions: Synergy 1: < 1.21.0-beta
Synergy 3: < 3.7.0-beta
Fixed in: Synergy 1: 1.21.0-beta
Synergy 3: 3.7.0-beta
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Server does not correctly close file descriptors for established TCP connections

high

Identifier: CVE-2021-42075
Affected versions: Synergy 1: < 1.21.0-beta
Synergy 3: < 3.7.0-beta
Fixed in: Synergy 1: 1.21.0-beta
Synergy 3: 3.7.0-beta
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Memory exhaustion in the server component

high

Identifier: CVE-2021-42076
Affected versions: Synergy 1: < 1.21.0-beta
Synergy 3: < 3.7.0-beta
Fixed in: Synergy 1: 1.21.0-beta
Synergy 3: 3.7.0-beta
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Privilege escalation through Daemon IPC server

high

Identifier: CVE-2026-41477
Affected versions: Synergy 1: >= 1.4.9, < 1.20.1
Synergy 3: < 3.6.1
Fixed in: Synergy 1: 1.20.1
Synergy 3: 3.6.1
CVSS: 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)

TLS multiplexer DoS on failed `SSL_accept`

high

Identifier: CVE-2026-44296
Affected versions: Synergy 1: <= 1.20.0
Synergy 3: < 3.6.1
Fixed in: Synergy 1: 1.20.1
Synergy 3: 3.6.1
CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

Clipboard deserialization global-buffer-overflow

medium

Identifier: CVE-2026-41476
Affected versions: Synergy 1: <= 1.20.0
Synergy 3: < 3.6.1
Fixed in: Synergy 1: 1.20.1
Synergy 3: 3.6.1
CVSS: Not scored

Denial of service causes the server to crash

medium

Identifier: CVE-2020-15117
Affected versions: Synergy 1: < 1.12.0
Fixed in: Synergy 1: 1.12.0
CVSS: Not scored