CVE-2026-3338 — aws-lc-sys
CVE-2026-3338 is a CWE-347 vulnerability in aws-lc-sys. A fix is available for aws-lc-sys — see the affected versions and patch details below.
PKCS7_verify Signature Validation Bypass in AWS-LC
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-3338.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
aws-lc-sysReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
AWS-LC is an open-source, general-purpose cryptographic library.
Impact
Improper signature validation in PKCS7_verify() in AWS-LC allows an unauthenticated user to bypass signature verification when processing PKCS7 objects with Authenticated Attributes.
Customers of AWS services do not need to take action. aws-lc-sys contains code from AWS-LC. Applications using aws-lc-sys should upgrade to the most recent release of aws-lc-sys.
Impacted versions:
aws-lc-sys versions: >= 0.24.0, < 0.38.0
Patches
The patch is included in v0.38.0
Workarounds
There is no workaround. Applications using aws-lc-sys should upgrade to the most recent release of aws-lc-sys.
Resources
If there are any questions or comments about this advisory, contact [AWS/Amazon] Security via the vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | aws-lc-sys | ≥ 0.24.0&&< 0.38.0 | 0.38.0cargo update -p aws-lc-sys --precise 0.38.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aws-lc-sys, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update aws-lc-sys to 0.38.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-3338 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-3338 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-3338. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Trusted Artifact Signer 1.3 | rhtas/tuffer-rhel9:1773307309 | RHSA-2026:5459 |
Frequently Asked Questions
Is CVE-2026-3338 in your dependencies?
O3 Security finds CVE-2026-3338 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.