# CVE-2025-9648: Denial of Service in CivetWeb

CVE-2025-9648 is fixed in 2 products on 1 platform, first by civetweb 1.15+dfsg-3ubuntu0.1~esm1, released September 29, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2025-9648
- Priority: High
- CVSS: n/a (Important)
- EPSS: 0.0076
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 29, 2025
- Weakness: Improper Neutralization of Null Byte or NUL Character
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-9648

## Description

A vulnerability in the CivetWeb library's function mg_handle_form_request allows remote attackers to trigger a denial of service (DoS) condition. By sending a specially crafted HTTP POST request containing a null byte in the payload, the server enters an infinite loop during form data parsing. Multiple malicious requests will result in complete CPU exhaustion and render the service unresponsive to further requests. This issue was fixed in commit 782e189. This issue affects only the library, standalone executable pre-built by vendor is not affected.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | civetweb Debian 13.5 (trixie) | 1.16+dfsg-2+deb13u1 | [DEBIAN-CVE-2025-9648](https://patchblox.com/security/data/fix/linux/debian-cve-2025-9648.md) | Sep 29, 2025 |
| Linux | civetweb Debian 14 | 1.16+dfsg-4 | [DEBIAN-CVE-2025-9648](https://patchblox.com/security/data/fix/linux/debian-cve-2025-9648.md) | Sep 29, 2025 |
| Linux | civetweb Ubuntu 22.04.1 LTS (jammy) | 1.15+dfsg-3ubuntu0.1~esm1 | [civetweb 1.15+dfsg-3ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-civetweb-1.15-dfsg-3ubuntu0.1-esm1.md) | Sep 29, 2025 |
| Linux | civetweb Ubuntu 24.04.5 LTS (noble) | 1.16+dfsg-1ubuntu0.1 | [civetweb 1.16+dfsg-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-civetweb-1.16-dfsg-1ubuntu0.1.md) | Sep 29, 2025 |
| Linux | civetweb Ubuntu 26.04.1 LTS (resolute) | 1.16+dfsg-3ubuntu0.1 | [civetweb 1.16+dfsg-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-civetweb-1.16-dfsg-3ubuntu0.1.md) | Sep 29, 2025 |
| Linux | libcivetweb1 Ubuntu 22.04.1 LTS (jammy) | 1.15+dfsg-3ubuntu0.1~esm1 | [libcivetweb1 1.15+dfsg-3ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libcivetweb1-1.15-dfsg-3ubuntu0.1-esm1.md) | Sep 29, 2025 |
| Linux | libcivetweb1 Ubuntu 24.04.5 LTS (noble) | 1.16+dfsg-1ubuntu0.1 | [libcivetweb1 1.16+dfsg-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libcivetweb1-1.16-dfsg-1ubuntu0.1.md) | Sep 29, 2025 |
| Linux | libcivetweb1 Ubuntu 26.04.1 LTS (resolute) | 1.16+dfsg-3ubuntu0.1 | [libcivetweb1 1.16+dfsg-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libcivetweb1-1.16-dfsg-3ubuntu0.1.md) | Sep 29, 2025 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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