CVE-2026-6040: the document foundation libreoffice Use After Free

Vulnerability summary

CVE-2026-6040 is a high (CVSS 7.3) Use After Free vulnerability in the document foundation libreoffice. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 5.7% of scored vulnerabilities.

Timeline

1. 15-06-2026
   PublishedVulnerability first disclosed.
2. 23-07-2026
   Last modifiedVulnerability information updated.

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.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.
• CWE-825Expired Pointer DereferenceThe product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.