CVE-2026-79591 libxls - Use After Free

libxls 1.6.3 contains a heap-buffer-overflow and use-after-free vulnerability caused by insufficient validation of a file-controlled font index in xls_getCSS(), letting attackers cause memory corruption or code execution, exploit requires crafted file input.

CVSS base score 7.8 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.17% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Use After Free
Impact
Remote Code Execution, Denial Of Service
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
10 September 2026
Updated
15 October 2026
Weakness
CWE-122

Vendor fix

Update to the latest version of libxls.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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