CVE-2026-33487: goxmldsig has validateSignature Loop Variable Capture Signature Bypass

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-26 · updated 2026-09-09
Weakness: CWE-347

Description

goxmlsig provides XML Digital Signatures implemented in Go. Prior to version 1.6.0, the `validateSignature` function in `validate.go` goes through the references in the `SignedInfo` block to find one that matches the signed element's ID. In Go versions before 1.22, or when `go.mod` uses an older version, there is a loop variable capture issue. The code takes the address of the loop variable `_ref` instead of its value. As a result, if more than one reference matches the ID or if the loop logic is incorrect, the `ref` pointer will always end up pointing to the last element in the `SignedInfo.References` slice after the loop. goxmlsig version 1.6.0 contains a patch.

Affected products

russellhaering goxmldsig: before 1.6.0 — fixed in 1.6.0

How to fix

Upgrade to a fixed version: russellhaering goxmldsig 1.6.0. Check the vendor advisory for mitigations.

References

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