CVE-2026-34577

HighPublic PoC

Published: 02 April 2026

Published

02 April 2026

Modified

07 April 2026

KEV Added

—

Patch

—

CVSS Score 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

EPSS Score 0.0016 36.0th percentile

Risk Priority 17 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-34577 is a high-severity SSRF (CWE-918) vulnerability in Gitroom Postiz. Its CVSS base score is 8.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 36.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

This vulnerability is AI-related — categorised as Other AI Platforms.

The strongest mitigations our analysis identified are NIST 800-53 AC-4 (Information Flow Enforcement) and SC-7 (Boundary Protection).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Requires validation of user-supplied URL inputs to prevent bypassable checks that enable SSRF exploitation.

AC-4 Information Flow Enforcement good match

prevent

Enforces information flow control policies to block server-initiated requests to internal services, localhost, or private network resources.

SC-7 Boundary Protection good match

preventdetect

Monitors and controls communications at system boundaries to restrict outbound proxy requests to unauthorized internal endpoints.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1552.005 Cloud Instance Metadata API Credential Access

Adversaries may attempt to access the Cloud Instance Metadata API to collect credentials and other sensitive data.

attack.mitre.org →

Why these techniques?

SSRF in unauthenticated public-facing endpoint (T1190) allows attackers to force server requests to internal resources including cloud metadata endpoints (T1522), leaking sensitive data.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

Postiz is an AI social media scheduling tool. Prior to version 2.21.3, the GET /public/stream endpoint in PublicController accepts a user-supplied url query parameter and proxies the full HTTP response back to the caller. The only validation is url.endsWith('mp4'), which…

is trivially bypassable by appending .mp4 as a query parameter value or URL fragment. The endpoint requires no authentication and has no SSRF protections, allowing an unauthenticated attacker to read responses from internal services, cloud metadata endpoints, and other network-internal resources. This issue has been patched in version 2.21.3.

Deeper analysisAI

CVE-2026-34577 is a server-side request forgery (SSRF) vulnerability, classified under CWE-918, affecting Postiz, an AI-powered social media scheduling tool. In versions prior to 2.21.3, the unauthenticated GET /public/stream endpoint in the PublicController accepts a user-supplied "url" query parameter and proxies the full HTTP response back to the caller. The sole validation checks if the URL ends with ".mp4", which can be easily bypassed by appending ".mp4" to the query parameter value or as a URL fragment.

Unauthenticated attackers can exploit this vulnerability remotely with low complexity and no privileges required, as indicated by the CVSS v3.1 base score of 8.6 (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N). By crafting a malicious URL that passes the weak validation, attackers can force the server to make requests to arbitrary internal services, cloud metadata endpoints like those on localhost or private IPs, and other network-internal resources, potentially leaking sensitive data through the proxied responses.

The vulnerability has been patched in Postiz version 2.21.3. Security practitioners should upgrade to this version or later. Additional details are available in the GitHub security advisory at https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-mv6h-v3jg-g539 and the release notes at https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.3.