# CVE-2025-34468: libcoap3: libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address...

CVE-2025-34468 is fixed in 8 products on 1 platform, first by DEBIAN-CVE-2025-34468, released December 31, 2025. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2025-34468
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0075
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Dec 31, 2025

## Description

libcoap versions up to and including 4.3.5, prior to commit 30db3ea, contain a stack-based buffer overflow in address resolution when attacker-controlled hostname data is copied into a fixed 256-byte stack buffer without proper bounds checking. A remote attacker can trigger a crash and potentially achieve remote code execution depending on compiler options and runtime memory protections. Exploitation requires the proxy logic to be enabled (i.e., the proxy request handling code path in an application using libcoap).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libcoap Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-debuginfo Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-debugsource Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-devel Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-doc Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-utils Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap-utils-debuginfo Fedora 43 | 4.3.5b-1.fc43 | [FEDORA-2026-0CE923A09D](https://patchblox.com/security/data/fix/linux/fedora-2026-0ce923a09d.md) | Apr 17, 2026 |
| Linux | libcoap3 Debian 13.5 (trixie) | 4.3.4-1.1+deb13u3 | [DEBIAN-CVE-2025-34468](https://patchblox.com/security/data/fix/linux/debian-cve-2025-34468.md) | Dec 31, 2025 |
| Linux | libcoap3 Debian 14 | 4.3.5-3 | [DEBIAN-CVE-2025-34468](https://patchblox.com/security/data/fix/linux/debian-cve-2025-34468.md) | Dec 31, 2025 |

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Data as of 2026-11-10T01:44:33Z 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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