| Package | Affected versions | Patched versions |
|---|---|---|
| github.com/xuri/excelize/v2 | ≥ 2.3.1, < 2.11.1-0.20260906004932-2badfcd5841d | 2.11.1-0.20260906004932-2badfcd5841d |
| excelize | ≥ 2.3.1, ≤ 2.11.0 |
Opening a file whose first eight bytes are the OLE magic number sends excelize down the decryption path whether or not the caller set a password, or supports encrypted workbooks at all. openReaderAt (excelize.go:198-215) branches on the header alone, and agileDecrypt calls convertPasswdToKey before the verifier hash is checked, so the key-derivation loop runs spinCount times regardless.
spinCount (crypt.go:98) is a plain int filled by a bare xml.Unmarshal of the file's own EncryptionInfo stream. Nothing bounds it.
A 3072-byte file with spinCount 100000000 makes OpenFile take 58.65s on v2.11.0 with default options, then return zip: not a valid zip file. It is linear at about 0.6 microseconds per iteration and the attacker picks the number, so 1e9 is roughly ten minutes. Nothing on the path takes a context.Context, so the caller cannot cancel it; in an HTTP handler the write timeout returns a response while the goroutine keeps spinning. Memory stays flat at 24 MB, so nothing reclaims it either.
v2.5.0 spinCount=10000000 5.307s
v2.9.1 spinCount=10000000 5.444s
v2.11.0 spinCount=10000000 7.529s
v2.11.0 spinCount=100000000 58.654s
The loop arrived with crypt.go in v2.3.1 and is unchanged through v2.11.0.
Excel and LibreOffice write spinCount 100000, which costs 61ms here, so a ceiling well above the legitimate value would cost real files nothing.
This is availability only, and it is not a vulnerability for a program that only opens files its own operator produced.
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