Off-by-One Vulnerability in Encrypted XLSX File Parser by xlnt-community
CVE-2026-2703

4.8MEDIUM

Key Information:

Vendor

Xlnt-community

Status
Xlnt
Vendor
CVE Published:
19 February 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-2703?

A vulnerability has been discovered in the xlnt-community xlnt Encrypted XLSX File Parser that affects the decoding function in base64 operations. This flaw can lead to an off-by-one error, resulting in potential exploitation if local access is obtained. The vulnerability stems from a manipulation within the source file responsible for cryptographic functions, specifically in the decode_base64 implementation. Publicly available exploit methods increase the urgency of this issue. Users are strongly advised to apply the provided patch, identified by commit f2d7bf494e5c52706843cf7eb9892821bffb0734, to mitigate any risks associated with this vulnerability.

Affected Version(s)

xlnt 1.6.0

xlnt 1.6.1

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-2703 - Proof of Concept

References

https://vuldb.com/?id.346649
vdb-entrytechnical-description
https://vuldb.com/?ctiid.346649
signaturepermissions-required
https://vuldb.com/?submit.754377
third-party-advisory

CVSS V4

Score:
4.8
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

Oneafter (VulDB User)
.