CVE-2019-11840
MEDIUMCVE-2019-11840 is a medium-severity (CVSS 5.9) Insufficient Random Values vulnerability in golang.org/x/crypto. O3 Security confirms whether CVE-2019-11840 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
golang.org/x/crypto/salsa20/salsa uses insufficiently random values
Blast Radius
golang.org/x/cryptoReal-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
An issue was discovered in the supplementary Go cryptography library, golang.org/x/crypto, before v0.0.0-20190320223903-b7391e95e576. A flaw was found in the amd64 implementation of the golang.org/x/crypto/salsa20 and golang.org/x/crypto/salsa20/salsa packages. If more than 256 GiB of keystream is generated, or if the counter otherwise grows greater than 32 bits, the amd64 implementation will first generate incorrect output, and then cycle back to previously generated keystream. Repeated keystream bytes can lead to loss of confidentiality in encryption applications, or to predictability in CSPRNG applications.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | golang.org/x/crypto | all versions | 0.0.0-20190320223903-b7391e95e576 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for golang.org/x/crypto. 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 golang.org/x/crypto to 0.0.0-20190320223903-b7391e95e576 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-11840 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-2019-11840 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-2019-11840. 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-2019-11840 in your dependencies?
O3 detects CVE-2019-11840 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.