CVE-2026-34576

HighPublic PoC

Published: 02 April 2026

Published

02 April 2026

Modified

07 April 2026

KEV Added

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Patch

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CVSS Score 7.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS Score 0.0004 12.2th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-34576 is a high-severity SSRF (CWE-918) vulnerability in Gitroom Postiz. Its CVSS base score is 7.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 12.2th 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 SC-7 (Boundary Protection) and SI-10 (Information Input Validation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 2 other techniques. 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 URLs to ensure they do not target internal resources, directly preventing SSRF exploitation in the upload-from-url endpoint.

SC-7 Boundary Protection good match

preventdetect

Monitors and controls communications at system boundaries to block unauthorized outbound requests to internal networks, cloud metadata, and services.

AC-4 Information Flow Enforcement partial match

prevent

Enforces information flow control policies that restrict application-initiated requests to approved external destinations only, mitigating SSRF access to internals.

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 →

T1522 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 →

T1046 Network Service Discovery Discovery

Adversaries may attempt to get a listing of services running on remote hosts and local network infrastructure devices, including those that may be vulnerable to remote software exploitation.

attack.mitre.org →

Why these techniques?

SSRF in public-facing /upload-from-url endpoint enables T1190 (exploiting public app for remote access); direct fetch of cloud instance metadata enables T1522; probing internal network resources enables T1046 (network service discovery).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Postiz is an AI social media scheduling tool. Prior to version 2.21.3, the POST /public/v1/upload-from-url endpoint accepts a user-supplied URL and fetches it server-side using axios.get() with no SSRF protections. The only validation is a file extension check (.png, .jpg,…

etc.) which is trivially bypassed by appending an image extension to any URL path. An authenticated API user can fetch internal network resources, cloud instance metadata, and other internal services, with the response data uploaded to storage and returned to the attacker. This issue has been patched in version 2.21.3.

Deeper analysisAI

CVE-2026-34576 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 POST /public/v1/upload-from-url endpoint allows authenticated users to supply a URL that the server fetches via axios.get() without any SSRF protections. The sole validation—a check for image file extensions like .png or .jpg—is easily bypassed by appending such an extension to any URL path.

An authenticated API user with low privileges (PR:L) can exploit this vulnerability remotely (AV:N) with low complexity (AC:L) and no user interaction (UI:N). Successful exploitation enables the attacker to fetch internal network resources, cloud instance metadata, and other internal services. The fetched response data is then uploaded to storage and returned directly to the attacker, resulting in high confidentiality impact (C:H) with a changed scope (S:C), as reflected in the CVSS v3.1 base score of 7.7.

The vulnerability has been patched in Postiz version 2.21.3. Security practitioners should upgrade to this version immediately. Additional details are available in the GitHub security advisory at https://github.com/gitroomhq/postiz-app/security/advisories/GHSA-89vp-m2qw-7v34 and the release notes at https://github.com/gitroomhq/postiz-app/releases/tag/v2.21.3.