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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| CivetWeb | CivetWeb | 1.10 – ≤ 1.16 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | civetweb | 1.16+dfsg-4 | — |
| Debian 13 | civetweb | 1.16+dfsg-2+deb13u1 | — |
| Debian 12 | civetweb | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | civetweb | No fix yet | — |
| Ubuntu 26.04 LTS | civetweb | 1.16+dfsg-3ubuntu0.1 | USN-8749-1 |
| Ubuntu 25.10 | civetweb | No fix yet | — |
| Ubuntu 24.04 LTS | civetweb | 1.16+dfsg-1ubuntu0.1 | USN-8749-1 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 22.04 LTS | civetweb | 1.15+dfsg-3ubuntu0.1~esm1 | USN-8749-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | ceph | 18.2.2-11 | — |
| Azure Linux 2 (CBL-Mariner) | ceph | 16.2.10-10 | — |
Advisories 2
- USN-8749-1 civetweb vulnerabilities Ubuntu Security Notices (USN) · Sep 14, 2026
- WID-SEC-2025-2668 Red Hat Enterprise Linux (CivetWeb library): Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Sep 13, 2026