Title: OpenSSL, Description: Resumen del problema: Cuando se procesa una CRL delta que contiene una extensión Indicador de CRL Delta, podría ocurrir una desreferencia de puntero NULL si falta la extensión Número de CRL requerida.

Resumen del impacto: Una desreferencia de puntero NULL puede desencadenar un fallo que lleva a una denegación de servicio para una aplicación.

Cuando el procesamiento de CRL y el procesamiento de CRL delta están habilitados durante la verificación de certificados X.509, el procesamiento de CRL delta no verifica si la extensión Número de CRL es NULL antes de desreferenciarla. Cuando se procesa un archivo CRL delta malformado, este parámetro puede ser NULL, causando una desreferencia de puntero NULL.

Explotar este problema requiere que la bandera X509_V_FLAG_USE_DELTAS esté habilitada en el contexto de verificación, que el certificado que se verifica contenga una extensión freshestCRL o que la CRL base tenga la bandera EXFLAG_FRESHEST establecida, y que un atacante proporcione una CRL malformada a una aplicación que la procese.

La vulnerabilidad se limita a la denegación de servicio y no puede escalarse para lograr la ejecución de código o la divulgación de memoria. Por esa razón, el problema se evaluó como de baja severidad según nuestra Política de Seguridad.

Los módulos FIPS en 3.6, 3.5, 3.4, 3.3 y 3.0 no se ven afectados por este problema, ya que el código afectado está fuera del límite del módulo FIPS de OpenSSL.

[{"vendor":"Siemens","product":"SIMATIC CN 4100","defaultStatus":"unknown","versions":[{"version":"0","lessThan":"V5.0","versionType":"custom","status":"affected"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 TM MFP - GNU/Linux subsystem","defaultStatus":"unknown","versions":[{"version":"0","lessThan":"*","versionType":"custom","status":"affected"}]}]

{"timestamp":"2026-04-10T20:18:04.195701Z","id":"CVE-2026-28388","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}

[{"vendor":"OpenSSL","product":"OpenSSL","defaultStatus":"unaffected","versions":[{"version":"3.6.0","lessThan":"3.6.2","versionType":"semver","status":"affected"},{"version":"3.5.0","lessThan":"3.5.6","versionType":"semver","status":"affected"},{"version":"3.4.0","lessThan":"3.4.5","versionType":"semver","status":"affected"},{"version":"3.3.0","lessThan":"3.3.7","versionType":"semver","status":"affected"},{"version":"3.0.0","lessThan":"3.0.20","versionType":"semver","status":"affected"},{"version":"1.1.1","lessThan":"1.1.1zg","versionType":"custom","status":"affected"},{"version":"1.0.2","lessThan":"1.0.2zp","versionType":"custom","status":"affected"}]}]

https://cert-portal.siemens.com/productcert/html/ssa-032379.html

https://cert-portal.siemens.com/productcert/html/ssa-265688.html

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

OR
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.0.0 up to (excluding) 3.0.20
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.3.0 up to (excluding) 3.3.7
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.4.0 up to (excluding) 3.4.5
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.5.0 up to (excluding) 3.5.6
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 3.6.0 up to (excluding) 3.6.2
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 1.0.2 up to (excluding) 1.0.2zp
          *cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:* versions from (including) 1.1.1 up to (excluding) 1.1.1zg

OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/59c3b3158553ab53275bbbccca5cb305d591cf2e Types: Patch

OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/5a0b4930779cd2408880979db765db919da55139 Types: Patch

OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/602542f2c0c2d5edb47128f93eac10b62aeeefb3 Types: Patch

OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/a9d187dd1000130100fa7ab915f8513532cb3bb8 Types: Patch

OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/d3a901e8d9f021f3e67d6cfbc12e768129862726 Types: Patch

OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260407.txt Types: Vendor Advisory

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

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.

CWE-476

https://github.com/openssl/openssl/commit/59c3b3158553ab53275bbbccca5cb305d591cf2e

https://github.com/openssl/openssl/commit/5a0b4930779cd2408880979db765db919da55139

https://github.com/openssl/openssl/commit/602542f2c0c2d5edb47128f93eac10b62aeeefb3

https://github.com/openssl/openssl/commit/a9d187dd1000130100fa7ab915f8513532cb3bb8

https://github.com/openssl/openssl/commit/d3a901e8d9f021f3e67d6cfbc12e768129862726

https://openssl-library.org/news/secadv/20260407.txt