CVE-2023-6865 Information disclosure in Firefox

What is CVE-2023-6865?

CVE-2023-6865 is a medium-severity vulnerability in Debian Debian Linux, published on 19 Dec 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

`EncryptingOutputStream` was susceptible to exposing uninitialized data. This issue could only be abused in order to write data to a local disk which may have implications for private browsing mode. This vulnerability affects Firefox ESR < 115.6 and Firefox < 121.

Which versions are affected by CVE-2023-6865?

It affects 3 products.

Products include Debian Debian Linux, Mozilla Firefox, Mozilla Firefox Esr.

How do I fix CVE-2023-6865?

Upgrade to a fixed version.

Is CVE-2023-6865 being exploited?

There is no known exploitation of CVE-2023-6865 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2023-6865, GHSA-5c8h-j5h5-r8w3, UBUNTU-CVE-2023-6865.