Is there a patch available for EUVD-2026-43040?

Yes, a patch is available for EUVD-2026-43040. Update the affected software to the latest version immediately.

Misskey EUVD-2026-43040

Q: What is the CVSS score of EUVD-2026-43040?

EUVD-2026-43040 has a CVSS 4.0 base score of 6.9 (Medium). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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. EPSS exploitation probability: 0.3%.

| CVE-2026-57575 MEDIUM

Server-Side Request Forgery (SSRF) (CWE-918)

2026-07-10 GitHub_M

SSRF Misskey Misskey Dev

6.9

CVSS 4.0 · Vendor: GitHub_M

Severity by source

Vendor (GitHub_M) PRIMARY

6.9 MEDIUM

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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

vuln.today AI

5.8 MEDIUM

Network-reachable with no auth (PR:N), scope changes to affect internal systems (S:C), blind SSRF causes low integrity impact on subsequent systems with no confirmed data exfiltration (C:N).

3.1 AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Jul 10, 2026 - 22:08 vuln.today

Patch available

Jul 10, 2026 - 22:02 EUVD

DescriptionCVE.org

Misskey is an open source, federated social media platform. Prior to 2026.6.0, Misskey contains a Server-Side Request Forgery (SSRF) vulnerability in URL preview functionality in UrlPreviewService. Due to missing network restrictions before establishing outbound connections, a remote attacker can cause the Misskey server to initiate HTTP requests to loopback, private, or link-local services. Because IP address validation takes place after the request has been sent and the process is subsequently rejected, no sensitive internal data is believed to be transmitted back or exposed to the attacker. This issue is fixed in version 2026.6.0.

AnalysisAI

Server-Side Request Forgery in Misskey's UrlPreviewService allows remote unauthenticated attackers to coerce the platform's backend into initiating outbound HTTP connections toward loopback addresses, RFC-1918 private ranges, and link-local networks. The root cause is that IP address validation is applied only after the TCP connection has already been established, meaning the outbound request reaches the internal target before the check rejects it. Per vendor disclosure, response data is not believed to be returned to the attacker, limiting the impact to blind SSRF with potential for triggering internal service side effects. No public exploit identified at time of analysis, and a fix is available in version 2026.6.0.

Technical ContextAI

Misskey (CPE: cpe:2.3:a:misskey-dev:misskey:*:*:*:*:*:*:*:*) is an ActivityPub-federated social media platform written in TypeScript, where URL preview generation is handled by the UrlPreviewService. The service fetches user-supplied URLs to generate link previews, a common feature requiring outbound HTTP. CWE-918 (Server-Side Request Forgery) applies here because the service fails to restrict outbound destinations before making the connection. Critically, the design flaw is a post-connection validation pattern: the server resolves the DNS name, opens a TCP connection, and dispatches the HTTP request before checking whether the resolved IP falls within restricted ranges. This TOCTOU-adjacent pattern means even a correctly structured deny-list fires too late to prevent the initial connection from reaching internal infrastructure.

RemediationAI

The primary fix is to upgrade Misskey to version 2026.6.0 or later, which corrects the post-connection IP validation order in UrlPreviewService (patch commit: https://github.com/misskey-dev/misskey/commit/1eac4ccf513a067b9f7b7d123057c09a389fccee). If immediate upgrade is not possible, a compensating control is to configure egress network filtering at the host or container level to block outbound connections from the Misskey process to RFC-1918 ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), loopback (127.0.0.0/8), and link-local (169.254.0.0/16) addresses - this moves the enforcement to the network layer where it cannot be bypassed by application-level timing issues. Trade-off: egress filtering may interfere with legitimate federation traffic if internal ActivityPub peers exist. Alternatively, disabling URL preview functionality entirely eliminates the attack surface at the cost of losing link previews site-wide. Consult the security advisory at https://github.com/misskey-dev/misskey/security/advisories/GHSA-jvcx-f39m-5xrj for full vendor guidance.