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CVE-2023-40549· NVD / CVE Program· CNA redhat

Shim: out-of-bounds read in verify_buffer_authenticode() malformed pe file

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.

MediumCVSS 5.5 · v3.1—No exploit Fix available

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Published
Jan 29, 2024
Updated
Jun 17, 2026
EPSS
0.4% · 33th percentile
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Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.5
CNA · redhat
6.2
0.7 point gap

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

VendorProduct
redhatshim
redhatenterprise linux
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora39
  • redhat enterprise linux8.0
  • redhat enterprise linux9.0
  • redhat shimbefore 15.8

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • Red Hat Red Hat Enterprise Linux 7

    • 0:15.8-3.el7 and laternot affected · rpm
    • 0:15.8-1.el7 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8

    • 0:15.8-4.el8_9 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.2 Advanced Update Support

    • 0:15.8-2.el8_2 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.2 Telecommunications Update Service

    • 0:15.8-2.el8_2 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.2 Update Services for SAP Solutions

    • 0:15.8-2.el8_2 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support

    • 0:15.8-2.el8_4 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.4 Telecommunications Update Service

    • 0:15.8-2.el8_4 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.4 Update Services for SAP Solutions

    • 0:15.8-2.el8_4 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support

    • 0:15.8-2.el8_6 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 8.8 Extended Update Support

    • 0:15.8-2.el8 and laternot affected · rpm
    • 0:15.8-2.el8 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 9

    • 0:15.8-4.el9_3 and laternot affected · rpm
  • Red Hat Red Hat Enterprise Linux 9.0 Extended Update Support

    • 0:15.8-3.el9 and laternot affected · rpm
    • 0:15.8-2.el9 and laternot affected · rpm
    • 0:15.8-2.el9 and laternot affected · rpm

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8shim-aa64before 15.8-4.el8_9.alma.115.8-4.el8_9.alma.1
AlmaLinux:8shim-ia32before 15.8-4.el8_9.alma.115.8-4.el8_9.alma.1
AlmaLinux:8shim-x64before 15.8-4.el8_9.alma.115.8-4.el8_9.alma.1
AlmaLinux:9shim-aa64before 15.8-4.el9_3.alma.115.8-4.el9_3.alma.1
AlmaLinux:9shim-x64before 15.8-4.el9_3.alma.115.8-4.el9_3.alma.1
Debian:10shimbefore 15.8-1~deb10u115.8-1~deb10u1
Debian:12shimbefore 15.8-1~deb12u115.8-1~deb12u1
Debian:13shimbefore 15.8-115.8-1
Red Hat:enterprise_linux:7::clientmokutilbefore 0:15.8-1.el70:15.8-1.el7
Red Hat:enterprise_linux:7::clientmokutil-debuginfobefore 0:15.8-1.el70:15.8-1.el7
Red Hat:enterprise_linux:7::clientshimbefore 0:15.8-3.el70:15.8-3.el7
Red Hat:enterprise_linux:7::clientshim-ia32before 0:15.8-1.el70:15.8-1.el7
Red Hat:enterprise_linux:7::clientshim-signedbefore 0:15.8-1.el70:15.8-1.el7
Red Hat:enterprise_linux:7::clientshim-unsigned-ia32before 0:15.8-3.el70:15.8-3.el7
Red Hat:enterprise_linux:7::clientshim-unsigned-x64before 0:15.8-3.el70:15.8-3.el7
Red Hat:enterprise_linux:7::clientshim-x64before 0:15.8-1.el70:15.8-1.el7
Red Hat:enterprise_linux:8::baseosshimbefore 0:15.8-4.el8_90:15.8-4.el8_9
Red Hat:enterprise_linux:8::baseosshim-aa64before 0:15.8-4.el8_90:15.8-4.el8_9
Red Hat:enterprise_linux:8::baseosshim-ia32before 0:15.8-4.el8_90:15.8-4.el8_9
Red Hat:enterprise_linux:8::baseosshim-x64before 0:15.8-4.el8_90:15.8-4.el8_9
Red Hat:enterprise_linux:9::baseosshimbefore 0:15.8-4.el9_30:15.8-4.el9_3
Red Hat:enterprise_linux:9::baseosshim-aa64before 0:15.8-4.el9_30:15.8-4.el9_3
Red Hat:enterprise_linux:9::baseosshim-x64before 0:15.8-4.el9_30:15.8-4.el9_3
Red Hat:rhel_aus:8.2::baseosshimbefore 0:15.8-2.el8_20:15.8-2.el8_2

+28

Other highest-scoring records for the same primary product.

  • CVE-2023-40547Shim: rce in http boot support may lead to secure boot bypass
    35Monitor
  • CVE-2014-3676Heap-based buffer overflow in Shim allows remote attackers to execute arbitrary code via a crafted IPv6 address, related to the "tftp:// DHC
    32Monitor
  • CVE-2022-28737There's a possible overflow in handle_image() when shim tries to load and execute crafted EFI executables
    31Monitor
  • CVE-2014-3677Unspecified vulnerability in Shim might allow attackers to execute arbitrary code via a crafted MOK list, which triggers memory corruption.
    31Monitor
  • CVE-2023-40548Shim: interger overflow leads to heap buffer overflow in verify_sbat_section on 32-bits systems
    29Monitor
  • CVE-2023-40550Shim: out-of-bound read in verify_buffer_sbat()
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:shim-aa6415.8-4.el8_9.alma.1 · AlmaLinux:8Package registry (OSV)
almalinux:shim-ia3215.8-4.el8_9.alma.1 · AlmaLinux:8Package registry (OSV)
almalinux:shim-x6415.8-4.el8_9.alma.1 · AlmaLinux:8Package registry (OSV)
debian:shim15.8-1~deb12u1 · Debian:12Package registry (OSV)
opensuse:shim15.8-150300.4.20.2 · openSUSE:Leap Micro 5.3Package registry (OSV)
red hat:mokutil0:15.8-1.el7 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:mokutil-debuginfo0:15.8-1.el7 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:shim0:15.8-2.el8_2 · Red Hat:rhel_aus:8.2::baseosPackage registry (OSV)
red hat:shim-aa640:15.8-3.el9 · Red Hat:rhel_eus:9.0::baseosPackage registry (OSV)
red hat:shim-ia320:15.8-2.el8_2 · Red Hat:rhel_aus:8.2::baseosPackage registry (OSV)
red hat:shim-signed0:15.8-1.el7 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:shim-unsigned-aarch640:15.8-2.el9 · Red Hat:rhel_eus:9.0::appstreamPackage registry (OSV)
red hat:shim-unsigned-ia320:15.8-3.el7 · Red Hat:enterprise_linux:7::clientPackage registry (OSV)
red hat:shim-unsigned-x640:15.8-2.el9 · Red Hat:rhel_eus:9.0::crbPackage registry (OSV)
red hat:shim-x640:15.8-2.el8_2 · Red Hat:rhel_aus:8.2::baseosPackage registry (OSV)
suse:pcr-oracle0.4.6-2.1 · SUSE:Linux Micro 6.0Package registry (OSV)
suse:shim15.8-150300.4.20.2 · SUSE:Linux Enterprise Micro 5.3Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2023-405500 days apartShim: out-of-bound read in verify_buffer_sbat()
    22Monitor
  • CVE-2023-405510 days apartShim: out of bounds read when parsing mz binaries
    20Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

All records