mcp-fetch through 1.6.3 Server-Side Request Forgery via Unstripped IPv6 Literal Brackets
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| kazuph | mcp-fetch | unaffected |
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No data.
No data.
| Vendor | Product | Versions | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Kazuph | Mcp-fetch |
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No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.351% probability within 30 days)
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Kazuph
Kazuph mcp-fetch |
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| Vendors & Products |
Kazuph
Kazuph mcp-fetch |
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
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| Type | Values Removed | Values Added |
|---|---|---|
| Description | mcp-fetch checks a fetch target against its SSRF guard without removing the brackets that surround an IPv6 literal. isSafeUrl reads the hostname from the parsed URL, which for a literal such as http://[::1]/ yields the bracketed string, and then tests it with net.isIP. That call returns zero for a bracketed value, so the branch holding the private-address checks is skipped entirely. The guard falls back to resolving the hostname, the bracketed string is not a resolvable name, no addresses are returned, and the target is reported safe. The HTTP client then strips the brackets and connects. Because the address may be given in IPv4-mapped form, the same path reaches any IPv4 target the loopback and private checks were meant to exclude, including link-local metadata endpoints. isPrivateIPv6 also has no case for the ::ffff: prefix, so the mapped form would still pass even if the brackets were removed. The fetch target is supplied as a tool argument, so an attacker who can influence what the model requests can read internal responses back into the model context. | |
| Title | mcp-fetch through 1.6.3 Server-Side Request Forgery via Unstripped IPv6 Literal Brackets | |
| Weaknesses | CWE-918 | |
| References |
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| Metrics |
cvssV3_1
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