s390/zcrypt: Improve EP11 CPRB domain handling with ASN.1 parsing

Summary

In the Linux kernel, the following vulnerability has been resolved: s390/zcrypt: Improve EP11 CPRB domain handling with ASN.1 parsing The zcrypt_msgtype6_send_ep11_cprb() function uses fragile struct overlays to access and modify the domain field in the EP11 CPRB payload, creating maintainability and security concerns: 1. Struct overlay approach (pld_hdr) assumes fixed payload structure and doesn't validate the actual ASN.1 encoding. 2. Complex length format detection logic is error-prone and doesn't properly validate bounds at each parsing step. 3. Direct struct member access bypasses proper ASN.1 validation. Fix by replacing struct overlays with explicit ASN.1 parsing that validates each field (payload tag/length, function tag/length/value, optional domain tag/length/value) with proper bounds checking at every step. Add asn1_int_encode() helper function to safely write integer values with correct endianness conversion. This makes the code consistent with the validation pattern introduced with the rework of the xcrb_msg_to_type6_ep11cprb_msgx() function.

Timeline

1. Aug 26, 2026, 2:37 PM UTCCVE published
2. Oct 16, 2026, 7:16 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 21, 2026, 12:46 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 20b0b0159390fa5c00a435195649680fefda81e0 · fixed in 00a44ff06bcffb68b9cd7e90d2259b7d14b82b18; From e2c6d91eb8b1533753755f07803e47eceed263d0 · fixed in db21b2cf6dd0af5ffd08931e0a9fcda5a0473220; From e2c6d91eb8b1533753755f07803e47eceed263d0 · fixed in 0864a163783bff109b548266921829ea794edc93; From 6.12.114 · fixed in 6.13

• Linux Linux

  7.1

• KernelLinux

  From 7.1.0 · fixed in 7.1.10

References 3