How severe is CVE-2026-42765?

CVE-2026-42765 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42765 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42765?

CVE-2026-42765 primarily affects Openssl. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-42765?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42765 have an EU (EUVD) identifier?

Yes. CVE-2026-42765 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35482.

When was CVE-2026-42765 published?

CVE-2026-42765 was published on 2026-06-09 and last updated on 2026-06-17.

CVE-2026-42765

CVE-2026-42765 is a high-severity vulnerability in Openssl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-35482
Weakness: CWE-476
Affected product: Openssl
Published: 2026-06-09
Last modified: 2026-06-17

Description

Issue summary: When a partial-chain certificate verification is enabled together with OCSP response checking for the whole chain, a NULL dereference will happen if the verified chain does not have a self-signed trusted anchor, crashing the process. Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application. When performing OCSP response checking for certificates in the verification chain, the code always tries to access the next certificate as the issuer. There is a check for a self-signed certificate. However with the partial chain verification enabled when the chain does not have a self-signed trusted anchor, the issuer will be NULL for the last certificate in the chain. A NULL pointer dereference then happens. This issue affects only applications which enable both OCSP verification of the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial chain verification (X509_V_FLAG_PARTIAL_CHAIN) in the certificate verification. Both flags are disabled by default. For that reason, we have assigned Low severity to the issue. No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.

Frequently asked questions

What is CVE-2026-42765?: Issue summary: When a partial-chain certificate verification is enabled together with OCSP response checking for the whole chain, a NULL dereference will happen if the verified chain does not have a self-signed trusted anchor, crashing the process. Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application. When performing OCSP response checking for certificates in the verification chain, the code always tries to access the next certificate as the issuer. There is a check for a self-signed certificate. However with the partial chain verification enabled when the chain does not have a self-signed trusted anchor, the issuer will be NULL for the last certificate in the chain. A NULL pointer dereference then happens. This issue affects only applications which enable both OCSP verification of the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial chain verification (X509_V_FLAG_PARTIAL_CHAIN) in the certificate verification. Both flags are disabled by default. For that reason, we have assigned Low severity to the issue. No FIPS modules are affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.
How severe is CVE-2026-42765?: CVE-2026-42765 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42765 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42765?: CVE-2026-42765 primarily affects Openssl. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-42765?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42765 have an EU (EUVD) identifier?: Yes. CVE-2026-42765 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35482.
When was CVE-2026-42765 published?: CVE-2026-42765 was published on 2026-06-09 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:4.0.0:-:*:*:*:*:*:*

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