What’s Vulnerable › Vulnerabilities

CVE-2026-2703: xlnt-community xlnt Encrypted XLSX File base64.cpp decode_base64 off-by-one

• Severity: medium (CVSS 5.5 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: 2026-02-19 · updated 2026-06-17
• Weakness: CWE-189

Description

A weakness has been identified in xlnt-community xlnt up to 1.6.1. Impacted is the function xlnt::detail::decode_base64 of the file source/detail/cryptography/base64.cpp of the component Encrypted XLSX File Parser. Executing a manipulation can lead to off-by-one. The attack requires local access. The exploit has been made available to the public and could be used for attacks. This patch is called f2d7bf494e5c52706843cf7eb9892821bffb0734. Applying a patch is advised to resolve this issue.

Affected products

• xlnt-community xlnt: through 1.6.1

References

• https://github.com/oneafter/0128/blob/main/xl1/repro
• https://github.com/xlnt-community/xlnt/
• https://github.com/xlnt-community/xlnt/commit/f2d7bf494e5c52706843cf7eb9892821bffb0734
• https://github.com/xlnt-community/xlnt/issues/137
• https://vuldb.com/?ctiid.346649
• https://vuldb.com/?id.346649
• https://vuldb.com/?submit.754377

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