Linux Kernel up to 7.1.9 s390/zcrypt zcrypt_msgtype6_send_ep11_cprb memory corruption

Summaryinfo

A vulnerability identified as very critical has been detected in Linux Kernel up to 7.1.9. Affected is the function zcrypt_msgtype6_send_ep11_cprb of the component s390/zcrypt. This manipulation causes memory corruption. This vulnerability is registered as CVE-2026-80544. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.1.9. It has been declared as very critical. Affected by this vulnerability is the function zcrypt_msgtype6_send_ep11_cprb of the component s390/zcrypt. The manipulation with an unknown input leads to a memory corruption vulnerability. The CWE definition for the vulnerability is CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-80544 since 08/26/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/26/2026).

Upgrading to version 7.1.10 eliminates this vulnerability. Applying the patch db21b2cf6dd0af5ffd08931e0a9fcda5a0473220/0864a163783bff109b548266921829ea794edc93 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.1.5
• 7.1.6
• 7.1.7
• 7.1.8
• 7.1.9

License

• open-source

Website

• Vendor: https://www.kernel.org/

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