CVE-2026-42327: Openssl :ocsp_responders For Certificates With Non-UTF-8 Vulnerability

HIGH
Advisory Identifier: GHSA-xp3w-r5p5-63rr
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CWE-20
Published
Advisory Summary

CVE-2026-42327 is a HIGH :ocsp_responders for certificates with non-utf-8 vulnerability (CWE-20: Improper Input Validation) affecting Openssl libraries in the crates.io ecosystem. The issue involves :ocsp_responders for certificates with non-utf-8 ocsp urls. Remediation is available by upgrading affected packages to version 0.10.79.

CVE-2026-42327 at a Glance

CVE Identifier CVE-2026-42327
GHSA Identifier GHSA-xp3w-r5p5-63rr
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-20: Improper Input Validation
Affected Product Openssl
Package Ecosystem crates.io
Published Date
Last Updated

How to Fix CVE-2026-42327

To remediate this vulnerability, upgrade all affected Openssl dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

openssl fixed: 0.10.79 
Upgrade openssl to 0.10.79
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for openssl

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-42327, inspect your project dependencies for Openssl:

inspect dependencies for openssl

Analyze the terminal output to locate any version of Openssl in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.10.79), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Openssl, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

`X509Ref::ocsp_responders` returns OCSP responder URLs from a certificate's AIA extension as `OpensslString`, whose `Deref<Target = str>` wraps the raw bytes with `str::from_utf8_unchecked`. OpenSSL does not enforce that the underlying IA5String is ASCII, so a certificate with non-UTF-8 bytes in its OCSP accessLocation causes safe Rust code to construct a `&str` that violates the UTF-8 invariant — resulting in undefined behavior.

CVE-2026-42327 Affected Openssl Versions

1 component(s)
Fixed Versions:
0.10.79
Product / Package Ecosystem Affected Versions Fixed Version
openssl
 crates.io
≥ 0.9.7
< 0.10.79
0.10.79

References

GitHub Advisory / Wiki ADVISORY
https://github.com/rust-openssl/rust-openssl/security/advisories/GHSA-xp3w-r5p5-63rr
NVD — CVE-2026-42327 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42327
Openssl Source Repository REPOSITORY
https://github.com/rust-openssl/rust-openssl

Frequently Asked Questions

What is CVE-2026-42327?
CVE-2026-42327 is a security vulnerability in Openssl involving :ocsp_responders for certificates with non-UTF-8 OCSP URLs under CWE-20: Improper Input Validation.
Which Openssl versions are affected?
Affected versions include releases prior to 0.10.79 across affected packages: openssl.
What version fixes CVE-2026-42327?
Upgrading to 0.10.79 (or the latest patched release for your respective branch) resolves the vulnerability.
Is openssl affected?
Yes, openssl is affected in releases prior to 0.10.79. Upgrade your dependency to 0.10.79 or later.
What CWE is associated with CVE-2026-42327?
CVE-2026-42327 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check crates.io dependencies for CVE-2026-42327?
Run the dependency tree command: 'inspect dependencies for openssl'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xp3w-r5p5-63rr",
  "modified" : "2026-05-15T23:45:53Z",
  "published" : "2026-05-05T21:46:38Z",
  "aliases" : [ "CVE-2026-42327" ],
  "summary" : "rust-openssl has undefined behavior in X509Ref::ocsp_responders for certificates with non-UTF-8 OCSP URLs",
  "details" : "`X509Ref::ocsp_responders` returns OCSP responder URLs from a certificate's AIA extension as `OpensslString`, whose `Deref<Target = str>` wraps the raw bytes with `str::from_utf8_unchecked`. OpenSSL does not enforce that the underlying IA5String is ASCII, so a certificate with non-UTF-8 bytes in its OCSP accessLocation causes safe Rust code to construct a `&str` that violates the UTF-8 invariant — resulting in undefined behavior.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "openssl"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.9.7"
      }, {
        "fixed" : "0.10.79"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rust-openssl/rust-openssl/security/advisories/GHSA-xp3w-r5p5-63rr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42327"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rust-openssl/rust-openssl"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-05T21:46:38Z",
    "nvd_published_at" : "2026-05-14T21:16:45Z"
  }
}