# DSA-5581-1: firefox-esr security update

DSA-5581-1, released December 20, 2023, fixes 1 CVE in firefox-esr. None of them is reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/fix/linux/dsa-5581-1
- Platform: Linux
- Released: Dec 20, 2023
- Priority: High (Closes CVE-2023-6856, high severity)
- CVEs: 1, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://security-tracker.debian.org/tracker/CVE-2023-6856

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [firefox-esr](https://patchblox.com/security/data/product/linux/firefox-esr.md) | Debian 11.6 (bullseye) | 115.6.0esr-1~deb11u1 |
| [firefox-esr](https://patchblox.com/security/data/product/linux/firefox-esr.md) | Debian 12.15 (bookworm) | 115.6.0esr-1~deb12u1 |

## CVEs this fix closes

| CVE | Priority | Title | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2023-6856](https://patchblox.com/security/data/cve/CVE-2023-6856.md) | High | Mozilla Firefox ESR and 5 others: The WebGL `DrawElementsInstanced` method was susceptible to a heap buffer overflow when used on systems… | 8.8 | 0.2063 |  |

---

Data as of 2026-11-07T06:34:28Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo