CVE-2026-6040: Heap use-after-free in ODF number-format blank-width parsing

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.2%

EPSS score, percentile 5 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

5.4 Medium

CVSS v4.0 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

• from 25.8 to before < 25.8.7
• from 26.2 to before < 26.2.3

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unknown.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

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.

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-6040 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 15 Jun 2026.
• The CVE record carries a CVSS v4.0 base score of 5.4 (Medium), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.2% (percentile 5), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

Heap use-after-free in ODF number-format blank-width parsing

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.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline