CVE-2026-33487
HIGHCVE-2026-33487 is a high-severity (CVSS 7.5) CWE-347 vulnerability in github.com/russellhaering/goxmldsig. O3 Security confirms whether CVE-2026-33487 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
goxmldsig has validateSignature Loop Variable Capture Signature Bypass
Blast Radius
github.com/russellhaering/goxmldsigReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/russellhaering/goxmldsig | all versions | 1.6.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/russellhaering/goxmldsig. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/russellhaering/goxmldsig to 1.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33487 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-33487 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-33487. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-33487 in your dependencies?
O3 detects CVE-2026-33487 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.