What is the CVSS score of CVE-2026-46556?

CVE-2026-46556 has a CVSS 3.1 base score of 6.5 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.0%.

FlaskBB CVE-2026-46556

MEDIUM

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

2026-05-21 https://github.com/flaskbb/flaskbb

GHSA-xq32-9g7q-7297

Microsoft Elastic Python SSRF

6.5

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.5 MEDIUM

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

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

Source Code Evidence Fetched

May 21, 2026 - 21:36 vuln.today

Analysis Generated

May 21, 2026 - 21:36 vuln.today

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

8 pypi packages depend on flaskbb (8 direct, 0 indirect)

Ecosystem-wide dependent count for version 2.2.0.

DescriptionGitHub Advisory

###Summary A Server-Side Request Forgery (SSRF) vulnerability in get_image_info() allows any authenticated user to force the server to send HTTP requests to arbitrary internal endpoints, including cloud metadata services (e.g., AWS 169.254.169.254). This is a blind SSRF with confirmed internal port scanning and internal API triggering capabilities. CVSS 6.5 Medium.

###Details In flaskbb/utils/helpers.py (line 571), the url parameter is passed directly to requests.get(url, stream=True) without any validation of scheme, host, or IP address.

python
# flaskbb/utils/helpers.py:571
def get_image_info(url: str):
    r = requests.get(url, timeout=(3.05, 27), stream=True)

Attack chain:

POST /user/settings/user-details (avatar URL)
→ ValidateAvatarURL.validate()
# validators.py:103
→ check_image(avatar)
# helpers.py:628
→ get_image_info(url)
# helpers.py:571
→ requests.get(url)
# No domain/IP restriction
Entry points:

/user/settings/user-details (any authenticated user)
/admin/users/<id>/edit (admin only)

###PoC submit.zip

Log in to FlaskBB as any user Navigate to Settings → User Details Enter http://169.254.169.254/latest/meta-data/ as the avatar URL Submit the form The server sends a GET request to the internal metadata endpoint

Three exploitation channels confirmed:

Server-side request: Captured on mock metadata server Internal port scan: check_image() returns distinct errors (CONN_REFUSED, NO_CONTENT_LENGTH, TYPE_NOT_ALLOWED, SUCCESS) that map internal network topology Internal API triggering: Mock APIs on 127.0.0.1:9200 triggered via SSRF (deploy, shutdown, key dump endpoints)

###Impact Any authenticated user is impacted. Attackers can force the server to request internal services, cloud metadata endpoints, or private network resources. On cloud deployments (AWS/GCP/Azure), IAM credentials can be leaked. In production, any GET-triggered internal service is reachable: CI/CD webhooks, Elasticsearch, etcd, Consul, etc.

AnalysisAI

Blind Server-Side Request Forgery in FlaskBB's avatar URL handling allows any authenticated user to force the server to issue arbitrary HTTP GET requests to internal network endpoints, including cloud instance metadata services (AWS IMDSv1 at 169.254.169.254, GCP, Azure equivalents). All versions up to and including 2.2.0 of the pip-distributed FlaskBB package are affected, with no vendor-released patch available at time of analysis. A proof-of-concept is publicly available via the GitHub Security Advisory, and three distinct exploitation channels have been demonstrated: direct credential exfiltration from cloud metadata services, internal port scanning via differential error responses, and triggering of internal APIs (Elasticsearch, etcd, Consul, CI/CD webhooks).

Technical ContextAI

FlaskBB is a Python-based forum application built on Flask. The vulnerability resides in flaskbb/utils/helpers.py at line 571, where the get_image_info() function accepts a URL string and passes it directly to Python's requests.get(url, stream=True) with no validation of URL scheme, hostname, or IP address range. The call chain is: POST /user/settings/user-details → ValidateAvatarURL.validate() in validators.py:103 → check_image() in helpers.py:628 → get_image_info() in helpers.py:571 → unrestricted requests.get(). The root cause class is CWE-918 (Server-Side Request Forgery), where user-controlled input is used to construct and execute a server-side HTTP request without allowlist or denylist controls. The CPE identifier is pkg:pip/flaskbb, indicating the vulnerability is in the PyPI-distributed package. A secondary exploitation channel arises because check_image() returns distinct error codes (CONN_REFUSED, NO_CONTENT_LENGTH, TYPE_NOT_ALLOWED, SUCCESS) that leak internal network topology, making this an oracle-assisted blind SSRF rather than a fully blind one.

RemediationAI

No vendor-released patch is available for CVE-2026-46556 at time of analysis - the GitHub Security Advisory confirms fixed version as None. Until a patch is released, operators should implement the following specific compensating controls. First, deploy a URL allowlist or denylist in the avatar URL validation path: modify ValidateAvatarURL.validate() in validators.py to reject requests targeting RFC-1918 private 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 addresses (169.254.0.0/16); this directly blocks cloud metadata and internal network targeting. Second, on AWS deployments, enforce IMDSv2 (hop limit 1, require session tokens) via EC2 instance metadata service configuration - this prevents token-less metadata retrieval even if SSRF reaches 169.254.169.254. Third, apply egress network controls at the host or container level to restrict outbound HTTP from the FlaskBB process to only required external domains. Fourth, disable avatar URL ingestion entirely (set the feature to disallow external URL avatars) if the functionality is non-essential - this eliminates the attack surface entirely with no SSRF residual. Monitor for advisory updates at https://github.com/flaskbb/flaskbb/security/advisories/GHSA-xq32-9g7q-7297.