langchain-ai/langchain · error · ValueError

Network error while validating URL: {e}

Error message

Network error while validating URL: {e}

What it means

While running `validate_safe_url`, a generic `OSError` (not a name-resolution `gaierror`) escaped the DNS-resolution step and was re-raised as `ValueError('Network error while validating URL: ...')`. This is an environment-level failure of `socket.getaddrinfo` — typically resolver unreachable, temporary failure in name resolution, or a socket-level resource problem — not a policy rejection.

Source

Thrown at libs/core/langchain_core/_security/_ssrf_protection.py:105

            hostname,
            parsed.port or (443 if parsed.scheme == "https" else 80),
            socket.AF_UNSPEC,
            socket.SOCK_STREAM,
        )

        for result in addr_info:
            ip_str: str = result[4][0]  # type: ignore[assignment]
            try:
                _validate_resolved_ip(ip_str, policy)
            except SSRFBlockedError as exc:
                raise ValueError(str(exc)) from exc

    except socket.gaierror as e:
        msg = f"Failed to resolve hostname '{hostname}': {e}"
        raise ValueError(msg) from e
    except OSError as e:
        msg = f"Network error while validating URL: {e}"
        raise ValueError(msg) from e

    return url_str


def is_safe_url(
    url: str | AnyHttpUrl,
    *,
    allow_private: bool = False,
    allow_http: bool = True,
) -> bool:
    """Non-throwing version of `validate_safe_url`."""
    try:
        validate_safe_url(url, allow_private=allow_private, allow_http=allow_http)
    except ValueError:
        return False
    else:
        return True

View on GitHub (pinned to e32fa9a52e)

Solutions

  1. Retry the validation after a short delay — EAI_AGAIN-style failures are often transient
  2. Inspect the embedded OS error text to distinguish 'resolver unreachable' from 'name unknown' and fix DNS config accordingly
  3. Point the process at a healthy resolver (set `nameserver` in /etc/resolv.conf, k8s DNS diagnostics) or a public resolver like 8.8.8.8 if policy allows
  4. If validation runs in a sandbox that forbids sockets, run SSRF validation outside the sandbox or against precomputed IPs

Example fix

# before
url = validate_safe_url(target)

# after
for attempt in range(3):
    try:
        url = validate_safe_url(target)
        break
    except ValueError as e:
        if attempt == 2 or not str(e).startswith("Network error"):
            raise
        time.sleep(2 ** attempt)
Defensive patterns

Strategy: retry

Try / catch

last: ValueError | None = None
for attempt in range(3):
    try:
        url = validate_safe_url(target)
        break
    except ValueError as e:
        if not str(e).startswith('Network error'):
            raise
        last, delay = e, 2 ** attempt
        time.sleep(delay)
else:
    raise RuntimeError(f'SSRF validation kept failing: {last}')

Prevention

When it happens

Trigger: `validate_safe_url(url)` when the system resolver is temporarily unavailable (e.g. 'Temporary failure in name resolution', EAI_AGAIN), DNS server timeouts, exhausted file descriptors affecting socket creation, or sandboxed environments blocking socket syscalls.

Common situations: Containers with flaky/unreachable DNS; AWS/ECS/K8s DNS pod failures; rate-limited resolvers (EAI_AGAIN under load); restrictive seccomp/sandbox profiles blocking `getaddrinfo`.

Related errors

AI-assisted analysis of langchain-ai/langchain@e32fa9a52e (2026-08-14). Data as JSON: /api/errors/8d6aca4ae5c99018. Report an issue: GitHub.