← Vulnerability feed

Vulnerability record · CVE-2026-28388 · published 7 April 2026

CVE-2026-28388: Openssl null pointer dereference vulnerability

OOpenssl · Openssl

Issue summary: When a delta CRL that contains a Delta CRL Indicator extension is processed a NULL pointer dereference might happen if the required CRL Number extension is missing. Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application. When CRL processing and delta CRL processing is enabled during X.509 certificate verification, the delta CRL processing does not check whether the CRL Number extension is NULL before dereferencing it. When a malformed delta CRL file is being processed, this parameter can be NULL, causing a NULL pointer dereference. Exploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in the verification context, the certificate being verified to contain a freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and an attacker to provide a malformed CRL to an application that processes it. The vulnerability is limited to Denial of Service and cannot be escalated to achieve code execution or memory disclosure. For that reason the issue was assessed as Low severity according to our Security Policy. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

7.5 CVSS 3.1 High EPSS 2.5% · top 15.9% CWE-476 · NULL pointer dereference
7.5CVSS 3.1 base score
2.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
24 Jul 2026Last modified by NVD

Description

Issue summary: When a delta CRL that contains a Delta CRL Indicator extension is processed a NULL pointer dereference might happen if the required CRL Number extension is missing. Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application. When CRL processing and delta CRL processing is enabled during X.509 certificate verification, the delta CRL processing does not check whether the CRL Number extension is NULL before dereferencing it. When a malformed delta CRL file is being processed, this parameter can be NULL, causing a NULL pointer dereference. Exploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in the verification context, the certificate being verified to contain a freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and an attacker to provide a malformed CRL to an application that processes it. The vulnerability is limited to Denial of Service and cannot be escalated to achieve code execution or memory disclosure. For that reason the issue was assessed as Low severity according to our Security Policy. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/openssl/openssl/commit/59c3b3158553ab53275bbbccca5cb305d591cf2e Patch
https://github.com/openssl/openssl/commit/5a0b4930779cd2408880979db765db919da55139 Patch
https://github.com/openssl/openssl/commit/602542f2c0c2d5edb47128f93eac10b62aeeefb3 Patch
https://github.com/openssl/openssl/commit/a9d187dd1000130100fa7ab915f8513532cb3bb8 Patch
https://github.com/openssl/openssl/commit/d3a901e8d9f021f3e67d6cfbc12e768129862726 Patch
https://openssl-library.org/news/secadv/20260407.txt Vendor Advisory
https://cert-portal.siemens.com/productcert/html/ssa-032379.html
https://cert-portal.siemens.com/productcert/html/ssa-265688.html

Track CVE-2026-28388 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.5CVE-2014-0160OpenSSL TLS/DTLS Heartbeat Extension Out-of-Bounds Read (Heartbleed)OpenSSL 1.0.1 before 1.0.1g mishandles Heartbeat Extension packets in its TLS and DTLS implementations, causing an out-of-bounds read of process memo…KEVEPSS 100%analysed10.0CVE-2009-3245Openssl improper input validation vulnerabilityOpenSSL before 0.9.8m does not check for a NULL return value from bn_wexpand function calls in (1) crypto/bn/bn_div.c, (2) crypto/bn/bn_gf2m.c, (3) c…EPSS 6.5%10.0CVE-2006-3738OpenSSL SSL_get_shared_ciphers buffer overflow via long cipher listOpenSSL versions before 0.9.7l and 0.9.8d contain a buffer overflow in the SSL_get_shared_ciphers function, triggered by a long list of ciphers. The …EPSS 49%analysed9.8CVE-2026-63073Openssl vulnerabilityIssue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name directly as the format string to `ERR_raise_da…EPSS 1.2%9.8CVE-2026-31789Openssl out-of-bounds write vulnerabilityIssue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer overflow on 32 bit platforms. Impact…EPSS 0.33%9.8CVE-2022-2274OpenSSL 3.0.4 RSA AVX512IFMA memory corruptionOpenSSL 3.0.4 introduced a bug in the RSA implementation for X86_64 CPUs supporting AVX512IFMA instructions, causing 2048-bit private key operations …EPSS 46%analysed9.8CVE-2021-3711OpenSSL SM2 decryption buffer overflowOpenSSL's SM2 decryption code miscalculates the output buffer size needed by EVP_PKEY_decrypt(), so the first sizing call can return a value smaller …EPSS 88%analysed9.8CVE-2016-6309OpenSSL 1.1.0a statem use-after-free on realloc in TLS session handlingOpenSSL 1.1.0a's statem/statem.c fails to account for memory-block movement after a realloc call, leaving a dangling pointer that can be used after f…EPSS 70%analysed

Source: NIST National Vulnerability Database (record CVE-2026-28388), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.