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Vulnerabilities

Security incident · CVE-2026-48818

SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows

Published May 23, 2026 · catalog updated May 28, 2026 · SSRF and NTLM credential

Last checked Nov 2, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-48818. EPSS is 0.37%. Act only if a listed version of SSRF and NTLM credential is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (SSRF and NTLM credential).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.37%
Remediation
Version ranges on file
Affected products
pip starlette

### Summary When serving static files on Windows, resolves the requested path with [ ](https://docs.python.org/3/library/os.path.html#os.path.realpath). If a UNC path (such as ) reaches the resolver, causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account's NTLMv2 credentials to the attacker-controlled host, which can then be cracked offline or relayed to other hosts. ### Details joins the requested path onto the served directory and calls [ ](https://docs.python.org/3/library/os.path.html#os.path.realpath) on the result before checking containment with [ ](https://docs.python.org/3/library/os.path.html#os.path.commonpath). On Windows, a UNC path is absolute, so [ ](https://docs.python.org/3/library/os.path.html#os.path.join) discards the served directory and resolves the bare UNC path, triggering the outbound SMB connection and NTLM authentication before the containment check rejects the path. The HTTP response is a benign 404, but the credential disclosure has already happened. POSIX systems are not affected. This only affects the default configuration ( ), which uses [ ](https://docs.python.org/3/library/os.path.html#os.path.realpath). The branch uses [ ](https://docs.python.org/3/library/os.path.html#os.path.abspath), which performs no I/O. ### Impact Applications running on Windows that serve files with (directly, or via a framework built on Starlette such as FastAPI) in the default configuration are affected. is typically unauthenticated, so any client can trigger the SMB connection and leak the service account's NTLMv2 hash. A secondary impact is discovering internal hosts reachable over SMB by timing responses for valid versus invalid addresses. ### Mitigation Applications not running on Windows are not affected. On Windows, serving static files through a dedicated web server (such as nginx or IIS) instead of avoids the issue. Blocking outbound SMB (port 445)

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • pip starlette< 1.1.0

How to fix CVE-2026-48818

  • Upgrade

    CVE-2026-48818 lists a fix boundary at 1.1.0. Compare the installed build with that boundary before you change production.

  • Version check

    Affected < 1.1.0

  • Advisory

    Open the inventory_github record and follow its fix.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-48818. EPSS is 0.37%. Act only if a listed version of SSRF and NTLM credential is installed.

Which versions are affected?

Compare what you have installed with < 1.1.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-918: Server-Side Request Forgery (SSRF). EPSS 0.37%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Nginx securityStarlette securityWindows security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 23, 2026 · Maintainer security tabs

    Detected

    ### Summary When serving static files on Windows, resolves the requested path with [ ](https://docs.python.org/3/library/os.path.html#os.path.realpath). If a UNC path (such as ) reaches the resolver, causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account's NTLMv2 credentials to the attacker-control

  2. May 28, 2026 · Maintainer security tabs

    Updated

    ### Summary When serving static files on Windows, resolves the requested path with [ ](https://docs.python.org/3/library/os.path.html#os.path.realpath). If a UNC path (such as ) reaches the resolver, causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account's NTLMv2 credentials to the attacker-control

Sources

  • Maintainer security tabsVendor advisoryGHSA-wqp7-x3pw-xc5r

    ### Summary When serving static files on Windows, resolves the requested path with [ ](https://docs.python.org/3/library/os.path.html#os.path.realpath). If a UNC path (such as ) reaches the resolver, causes the process to open a connection to the remote host over SMB (port 445). This is a server-side request forgery (SSRF) that leaks the service account's NTLMv2 credentials to the attacker-control

    github.com

Freshness

Last verified in this catalog Nov 2, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Maintainer security tabsNov 2, 2026