CVE-2026-42327 — rust-openssl has undefined behavior in openssl —...

HIGH

rust-openssl has undefined behavior in X509Ref::ocsp_responders for certificates with non-UTF-8 OCSP URLs

Published May 5, 2026Updated September 10, 2026Source: osv

Summary

`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.

Advisory Timeline

First published May 5, 2026 (160 days ago).
Last revised September 10, 2026 — 127 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Cargo

Update openssl to 0.10.79 or later

cargo update -p openssl --precise 0.10.79

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: crates.io (1).

Package	Ecosystem	Affected	Fixed In
openssl	crates.io	All versions	0.10.79

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-20
Improper Input ValidationMITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 7.5 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

—

Confidentiality

—

Integrity

—

Availability

—

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

References

Frequently Asked Questions

What is CVE-2026-42327?: rust-openssl has undefined behavior in X509Ref::ocsp_responders for certificates with non-UTF-8 OCSP URLs This vulnerability has been assigned a severity rating of HIGH (CVSS score: 7.5/10).
How do I check if my project is affected by CVE-2026-42327?: CVE-2026-42327 affects openssl. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-42327 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

7.5

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-xp3w-r5p5-63rr

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