CVE-2026-3663: xlnt-community xlnt XLSX File compound_document.cpp xsgetn out-of-bounds

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-07 · updated 2026-06-17
Weakness: CWE-119

Description

A vulnerability was found in xlnt-community xlnt up to 1.6.1. This issue affects the function xlnt::detail::compound_document_istreambuf::xsgetn of the file source/detail/cryptography/compound_document.cpp of the component XLSX File Parser. Performing a manipulation results in out-of-bounds read. The attack is only possible with local access. The exploit has been made public and could be used. The patch is named 147. It is recommended to apply a patch to fix this issue.

Affected products

xlnt-community xlnt: through 1.6.1

References

https://github.com/oneafter/0128/blob/main/xl3/repro
https://github.com/xlnt-community/xlnt/
https://github.com/xlnt-community/xlnt/issues/139
https://github.com/xlnt-community/xlnt/pull/147
https://vuldb.com/?ctiid.349552
https://vuldb.com/?id.349552
https://vuldb.com/?submit.764644

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