CVE-2026-6040 Heap use-after-free in ODF number-format blank-width parsing
A heap use-after-free in LibreOffice allows attackers to execute arbitrary code or cause denial of service via a malformed ODF number format.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-6040?
CVE-2026-6040 is a medium-severity use after free vulnerability in The Document Foundation LibreOffice, published on 15 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
A heap use-after-free existed when importing the blank-width characters of an ODF number format. A position value read from the document was not checked against the length of the format-code string, so a malformed number format could be processed against memory outside that string. In fixed versions the position is bounds-checked before use.
Which versions are affected by CVE-2026-6040?
How do I fix CVE-2026-6040?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-6040 being exploited?
There is no known exploitation of CVE-2026-6040 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-6040, GHSA-pp4w-c8m6-4xvf, UBUNTU-CVE-2026-6040.