EUVD-2026-26402Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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ReconPosition network for MITM
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DeliveryIntercept TLS handshake
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ExploitPresent revoked certificate with crafted multi-record OCSP response
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InstallTrigger OCSP parser logic error
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C2Client incorrectly validates revoked cert
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ExecuteComplete TLS handshake as MITM
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ImpactAccess application plaintext
Vulnerability Assessment
| Weakness |
CWE
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| Exploitation Conditions | OCSP verification must be explicitly enabled in the GnuTLS client configuration - this is not a default behavior in all applications and requires deliberate enablement of certificate status checking. The attacker must be able to perform a MITM attack on the TLS handshake, giving them the ability to intercept and modify the OCSP response sent during negotiation; this requires network-level access on the path between client and server (e.g., ARP spoofing, DNS redirection, or network position). The attacker must possess or have access to a revoked X.509 certificate (one previously issued by a trusted CA and later revoked), which they can present to the client. The OCSP response sent by the attacker must be crafted to span multiple TLS records in a specific manner that triggers the parser logic error; this requires detailed knowledge of the vulnerability or availability of exploit code. Non-default configurations that disable OCSP checking (such as applications that only use CRL-based revocation or no revocation checking at all) are not vulnerable to this specific attack. |
| Impact | Despite the low CVSS score of 3.7, this vulnerability poses a meaningful trust compromise risk. The CVSS vector (AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N) indicates network-accessible exploitation with high complexity, unauthenticated access, and no user interaction required, but with limited confidentiality impact and no integrity or availability impact directly from the OCSP logic error. However, the real-world risk is elevated by the nature of the flaw: an attacker who successfully exploits this gains the ability to present a revoked certificate that a TLS client will incorrectly trust, enabling Man-in-the-Middle (MITM) attacks against connections where the server certificate has been revoked. The high attack complexity likely reflects the requirement to craft a specific multi-record response structure that triggers the parsing flaw, and the necessity for the client to have OCSP verification explicitly enabled. This is not a widespread vulnerability affecting all GnuTLS deployments - only those with OCSP stapling or OCSP validation enabled, which is not the default configuration in all contexts. The vulnerability is a logic error rather than a memory-safety issue, reducing the likelihood of unintended secondary impacts. No KEV listing or public exploit code exists, suggesting no active exploitation at the time of analysis, though the specific nature of the attack (MITM during TLS negotiation) may limit visibility into real-world incidents. Organizations using OCSP for certificate revocation checking should prioritize patching; those relying on CRL or other revocation mechanisms may face lower immediate risk, though certificate revocation is a critical trust mechanism. |
| Exploit ScenarioDerived | An attacker positioned to perform MITM attacks on TLS connections (e.g., on the same network, via DNS hijacking, or BGP hijacking) observes a TLS client initiating a connection to a server and intercepts the handshake. The attacker presents a revoked server certificate (one previously issued by a trusted CA but later revoked), along with a specially crafted multi-record OCSP response that exploits the parsing logic flaw in GnuTLS. The client, configured to validate OCSP status, incorrectly processes the malformed response and accepts the revoked certificate as valid, allowing the attacker to complete the TLS handshake and decrypt or modify the subsequent application traffic. |
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Alert meAnalysisAIv1 – Apr 30, 2026
GnuTLS with OCSP verification enabled incorrectly accepts revoked server certificates when presented with specially crafted multi-record OCSP responses during TLS handshakes, allowing attackers to bypass certificate revocation checks and establish connections to compromised servers. The vulnerability requires high attack complexity and specific OCSP configuration, affecting Red Hat Enterprise Linux 6-10, Red Hat Hardened Images, and OpenShift Container Platform 4. No public exploit code or active exploitation has been identified at the time of analysis.
RemediationAI
Apply Red Hat security updates for GnuTLS across affected systems using the vendor-provided errata for RHEL 6, 7, 8, 9, and 10, with specific patch versions available through Red Hat's advisory portal (https://access.redhat.com/security/cve/CVE-2026-3832). For OpenShift Container Platform 4 deployments, update the platform and rebuild container images with patched GnuTLS. As an interim compensating control, disable OCSP verification on affected clients if the security posture permits, though this weakens certificate revocation checking and should only be temporary; alternatively, enforce CRL-based revocation checking instead of OCSP if supported by the application. Network-level MITM prevention (such as pinning or explicit firewall rules limiting certificate issuance paths) can reduce the window of exposure for the specific attack scenario, but cannot fully mitigate the OCSP validation bypass itself. Monitor upstream GnuTLS releases and Red Hat advisories for patched version numbers, as this CVE was assigned in 2026 and patch availability timelines may not yet be final.
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Technical ContextAI · show details
GnuTLS is a cryptographic library that implements TLS/SSL and DTLS protocols, including support for Online Certificate Status Protocol (OCSP) validation. OCSP is a mechanism for checking X.509 digital certificate revocation status in real-time, as an alternative to Certificate Revocation Lists (CRLs). The vulnerability stems from a logic error (CWE-179: Improper Neutralization of Formula Elements in a CSV File) in how GnuTLS parses and validates multi-record OCSP responses - responses that span multiple TLS records during the handshake. The affected CPE entries indicate the vulnerability impacts GnuTLS bundled with Red Hat Enterprise Linux versions 6 through 10, Red Hat Hardened Images, and OpenShift Container Platform 4, spanning both older legacy systems and modern containerized deployments.
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Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Primary rating from Vendor (redhat) · only source for this CVE.
CVSS VectorVendor: redhat
DescriptionCVE.org
A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted Online Certificate Status Protocol (OCSP) response during a TLS handshake. Due to a logic error in how gnutls processes multi-record OCSP responses, a client with OCSP verification enabled may incorrectly accept a revoked server certificate, potentially leading to a compromise of trust.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
Affected Products (CPE)CVE.org
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