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CVE-2026-4428 — aws-lc-fips-sys

CVE-2026-4428 is a CWE-299 vulnerability in aws-lc-fips-sys. A fix is available for aws-lc-fips-sys — see the affected versions and patch details below.

CRL Distribution Point Scope Check Logic Error in AWS-LC

Also known asGHSA-9f94-5g5w-gf6rRUSTSEC-2026-0042RUSTSEC-2026-0048
Published
Mar 19, 2026
Updated
Aug 12, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • 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-2026-4428.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs17th percentile — riskier than 17% of all scored CVEsHighest risk

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

2 pkgs affected
🦀aws-lc-fips-sys🦀aws-lc-sys

Real-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

A logic error in CRL distribution point matching in AWS-LC allows a revoked certificate to bypass revocation checks during certificate validation, when the application enables CRL checking and uses partitioned CRLs with Issuing Distribution Point (IDP) extensions.

Customers of AWS services do not need to take action. aws-lc-sys and aws-lc-fips-sys contain code from AWS-LC. Applications using aws-lc-sys or aws-lc-fips-sys should upgrade to the most recent releases of aws-lc-sys or aws-lc-fips-sys.

Impacted versions:

  • aws-lc-sys >= v0.15.0, < v0.39.0
  • aws-lc-fips-sys >= v0.13.0, < v0.13.13

Patches

The patch is included in aws-lc-sys v0.39.0 and aws-lc-fips-sys v0.13.13.

Workarounds

Applications can workaround this issue if they do not enable CRL checking (X509_V_FLAG_CRL_CHECK). Applications using complete (non-partitioned) CRLs without IDP extensions are also not affected.

Otherwise, there is no workaround and applications using aws-lc-sys or aws-lc-fips-sys should upgrade to the most recent releases of aws-lc-sys or aws-lc-fips-sys.

References

If you have any questions or comments about this advisory, we ask that you contact AWS Security via our vulnerability reporting page or directly via email to [email protected]. Please do not create a public GitHub issue.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.ioaws-lc-fips-sys≥ 0.13.0&&< 0.13.130.13.13cargo update -p aws-lc-fips-sys --precise 0.13.13
🦀crates.ioaws-lc-sys≥ 0.15.0&&< 0.39.00.39.0cargo update -p aws-lc-sys --precise 0.39.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aws-lc-fips-sys, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update aws-lc-fips-sys to 0.13.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4428 is resolved across your whole dependency graph.

  3. 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.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-4428 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-4428. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary AWS-LC is an open-source, general-purpose cryptographic library. ### Impact A logic error in CRL distribution point matching in AWS-LC allows a revoked certificate to bypass revocation checks during certificate validation, when the application enables CRL checking and uses partitioned CRLs with Issuing Distribution Point (IDP) extensions. Customers of AWS services do not need to take action. aws-lc-sys and aws-lc-fips-sys contain code from AWS-LC. Applications using aws-lc-sys or aws-lc-fips-sys should upgrade to the most recent releases of aws-lc-sys or aws-lc-fips-sys. ###
O3 Security · Impact-Aware SCA

Is CVE-2026-4428 in your dependencies?

O3 Security finds CVE-2026-4428 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works
CVE-2026-4428: aws-lc-fips-sys | O3 Security