shim-signed-15.8-1.el7, shim-15.8-3.el7

The shim package contains a first-stage UEFI boot loader that handles chaining to a trusted full boot loader under secure boot environments.

Security Fix(es):

shim: RCE in http boot support may lead to Secure Boot bypass (CVE-2023-40547)
shim: Interger overflow leads to heap buffer overflow in verify_sbat_section on 32-bits systems (CVE-2023-40548)
shim: Out-of-bounds read printing error messages (CVE-2023-40546)
shim: Out-of-bounds read in verify_buffer_authenticode() malformed PE file (CVE-2023-40549)
shim: Out-of-bound read in verify_buffer_sbat() (CVE-2023-40550)
shim: out of bounds read when parsing MZ binaries (CVE-2023-40551)

CVEs:
CVE-2023-40546
A flaw was found in Shim when an error happened while creating a new ESL variable. If Shim fails to create the new variable, it tries to print an error message to the user; however, the number of parameters used by the logging function doesn't match the format string used by it, leading to a crash under certain circumstances.
CVE-2023-40547
A remote code execution vulnerability was found in Shim. The Shim boot support trusts attacker-controlled values when parsing an HTTP response. This flaw allows an attacker to craft a specific malicious HTTP request, leading to a completely controlled out-of-bounds write primitive and complete system compromise. This flaw is only exploitable during the early boot phase, an attacker needs to perform a Man-in-the-Middle or compromise the boot server to be able to exploit this vulnerability successfully.
CVE-2023-40548
A buffer overflow was found in Shim in the 32-bit system. The overflow happens due to an addition operation involving a user-controlled value parsed from the PE binary being used by Shim. This value is further used for memory allocation operations, leading to a heap-based buffer overflow. This flaw causes memory corruption and can lead to a crash or data integrity issues during the boot phase.
CVE-2023-40549
An out-of-bounds read flaw was found in Shim due to the lack of proper boundary verification during the load of a PE binary. This flaw allows an attacker to load a crafted PE binary, triggering the issue and crashing Shim, resulting in a denial of service.
CVE-2023-40550
An out-of-bounds read flaw was found in Shim when it tried to validate the SBAT information. This issue may expose sensitive data during the system's boot phase.
CVE-2023-40551
A flaw was found in the MZ binary format in Shim. An out-of-bounds read may occur, leading to a crash or possible exposure of sensitive data during the system's boot phase.