# CVE-2026-46527: Null dereference in cpp-httplib

> An attacker can crash the server by sending a malformed X-Forwarded-For header when trusted proxies are configured, causing a null dereference.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 May 2026
- **Updated:** 1 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-46527, GHSA-hg3g-vrg8-578g, UBUNTU-CVE-2026-46527

## What is CVE-2026-46527?

CVE-2026-46527 is a high-severity vulnerability in yhirose cpp-httplib, published on 29 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, When the server has called Server::set_trusted_proxies() with a non-empty trusted-proxy list, an attacker can send an HTTP request that includes an X-Forwarded-For header whose value parses to no valid IP segments. The code path then executes get_client_ip(), which calls front() on an empty std::vector—undefined behavior in C++. On typical implementations this manifests as abnormal process termination (denial of service). With Sanitizers enabled, you get an explicit runtime diagnostic. This vulnerability is fixed in 0.44.0.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-46527?

It affects 1 product.


Products: Yhirose Cpp-Httplib.

## How do I fix CVE-2026-46527?

Upgrade to a fixed version.

## Is CVE-2026-46527 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46527 exists.

## Other vulnerabilities in yhirose cpp-httplib

- [CVE-2025-66570](https://insights.sbomify.com/CVE-2025-66570/): cpp-httplib Untrusted HTTP Header Handling: Internal Header Shadowing (REMOTE*/LOCAL*) (critical 10.0)
- [CVE-2026-45372](https://insights.sbomify.com/CVE-2026-45372/): cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection (critical 9.9)
- [CVE-2026-32627](https://insights.sbomify.com/CVE-2026-32627/): cpp-httplib has a Silent TLS Certificate Verification Bypass on HTTPS Redirect via Proxy (high 8.7)
- [CVE-2026-22776](https://insights.sbomify.com/CVE-2026-22776/): cpp-httplib vulnerable to a denial of service (DOS) using a zip bomb (high 8.7)
- [CVE-2026-21428](https://insights.sbomify.com/CVE-2026-21428/): cpp-httplib has CRLF injection in http headers (high 7.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-46527 and fix it if it is affected.

What it is: CVE-2026-46527 is a high-severity vulnerability in yhirose cpp-httplib, published on 29 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46527 exists.

Affected product: yhirose cpp-httplib. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-46527/ (Markdown: https://insights.sbomify.com/CVE-2026-46527/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46527
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46527
- OSV: https://osv.dev/vulnerability/CVE-2026-46527

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-46527/
Summaries are generated and may contain mistakes; the official description above is the record.