fix: ctype UB, WebSocket over-read, stoi crash, signed shift UB, proto pollution

[VirajMishra1]

fix: ctype UB, WebSocket over-read, stoi crash, shift UB, proto pollution

Six correctness and safety fixes across four files:

1. src/inspector_io.cc:381 -- isdigit called on plain char (undefined behavior)

::isdigit is defined only for values representable as unsigned char or EOF.
Passing a plain char (which may be negative on platforms where char is signed)
is undefined behavior. Fixed with an (unsigned char) cast in the lambda.

2. src/inspector_socket.cc:363 -- WebSocket extended-frame buffer over-read

The extended-payload-length bounds check used buffer.size() - kMaskingKeyWidthInBytes
as the minimum remaining bytes, but buffer is the full original buffer while
it may already have advanced into it. On a crafted extended-length frame,
payload_length bytes could be read past the end of the available data.
Fixed to check buffer.end() - it (remaining bytes from current position).

3. src/inspector_io.cc:383 -- std::stoi throws on out-of-range port strings

std::stoi throws std::out_of_range for digit-only strings that exceed INT_MAX
(e.g. "99999999999" passes the isdigit check but crashes). Added
try/catch (std::exception&) to handle both invalid_argument and out_of_range.

4. src/inspector_io.cc:386 -- signed left shift is undefined behavior

target_session_id << 16 on a signed int is UB if the result overflows.
Fixed with static_cast<unsigned int>(target_session_id) << 16.

5. lib/_http_outgoing.js:287 -- prototype-inheriting header dict

const headers = {} in _renderHeaders() creates an object that inherits
from Object.prototype. Header names are user-controlled strings; a header named
__proto__ or toString can shadow prototype properties.
Fixed to { __proto__: null }.

6. lib/os.js:219 -- prototype-inheriting network interface dict

Same issue in networkInterfaces(): the result object is keyed by OS interface
names. Fixed to { __proto__: null }.

[nodejs-github-bot]

Review requested:

• @nodejs/http
• @nodejs/inspector
• @nodejs/net

[MikeMcC399]

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[MikeMcC399]

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[VirajMishra1]

I have read and understood all of the linked documents -- the contributing guide, pull request guide, AI use policy, automation policy, and Code of Conduct.

To be transparent: I used AI tooling to help identify these bugs and draft the initial code, but I personally reviewed each change, understand what it does, and take responsibility for it. I did not use automated tooling to open this PR -- I opened it manually after reviewing the diff. Happy to discuss any of the specific changes if that would help.

[MikeMcC399]

Please check the CI failures for your PR. You can view them under

https://github.com/nodejs/node/actions?query=actor%3AVirajMishra1+is%3Afailure

You should make sure that your changes run successfully locally. See https://github.com/nodejs/node/blob/main/doc/contributing/pull-requests.md#step-6-test

[VirajMishra1]

Thanks for checking. Two CI failures, both now fixed:

1. Build failures (inspector_io.cc): The try/catch around std::stoi doesn't compile when -fno-exceptions is set. Replaced with std::from_chars (C++17, no exceptions needed, same overflow-safe behavior).

2. Commit message lint: The title used fix: which isn't a valid Node.js subsystem prefix. Amended to inspector,http,os: fix ctype UB, stoi overflow, proto pollution (within 72 chars, valid subsystems, with Signed-off-by trailer).

Force-pushed the updated commit. CI should be clean now.