# CVE-2025-53629: cpp-httplib Unbounded Memory Allocation in Chunked/No-Length Requests Vulnerability

> Attackers can exhaust server memory via chunked requests in cpp-httplib, causing denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Jul 2025
- **Updated:** 10 Jul 2025
- **Also known as:** DEBIAN-CVE-2025-53629, ECHO-39ee-6c8b-c400, OESA-2025-1839, OESA-2025-1840, OESA-2025-1841, OESA-2025-1842, OESA-2025-1843, UBUNTU-CVE-2025-53629

## What is CVE-2025-53629?

CVE-2025-53629 is a high-severity denial of service vulnerability in yhirose cpp-httplib, published on 10 Jul 2025. 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 0.23.0, incoming requests using Transfer-Encoding: chunked in the header can allocate memory arbitrarily in the server, potentially leading to its exhaustion. This vulnerability is fixed in 0.23.0. NOTE: This vulnerability is related to CVE-2025-53628.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2025-53629?

It affects 1 product.


Products: Yhirose Cpp-Httplib.

## How do I fix CVE-2025-53629?

Upgrade to a fixed version.

## Is CVE-2025-53629 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-53629 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-2026-46527](https://insights.sbomify.com/CVE-2026-46527/): Null dereference in cpp-httplib (high 8.7)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-53629 and fix it if it is affected.

What it is: CVE-2025-53629 is a high-severity denial of service vulnerability in yhirose cpp-httplib, published on 10 Jul 2025. 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-2025-53629 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-2025-53629/ (Markdown: https://insights.sbomify.com/CVE-2025-53629/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-53629
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-53629
- OSV: https://osv.dev/vulnerability/CVE-2025-53629

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-53629/
Summaries are generated and may contain mistakes; the official description above is the record.