CVE-2023-40547: Shim: rce in http boot support may lead to secure boot bypass
Noroxi assessment
Priority: Monitor (action score 35/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 5.4% (FIRST EPSS); higher than 92.6% of all records.
- Someone on the same network segment can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
- Fixed version: shim-aa64 (AlmaLinux:8) 15.8-4.el8_9.alma.1; shim-ia32 (AlmaLinux:8) 15.8-4.el8_9.alma.1; shim-x64 (AlmaLinux:8) 15.8-4.el8_9.alma.1.
Low priority for now. Upgrade to shim-aa64 (AlmaLinux:8) 15.8-4.el8_9.alma.1; shim-ia32 (AlmaLinux:8) 15.8-4.el8_9.alma.1; shim-x64 (AlmaLinux:8) 15.8-4.el8_9.alma.1 or later.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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.
- Published
- Jan 25, 2024
- Updated
- Jun 26, 2026
- EPSS
- 5.4% · 92th percentile
- CWE
- CWE-787
Report tools
Action score
35
Monitor
Low priority for now.
- CVSS
- 33 / 40 · 8.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 2 / 30 · 5.4%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- 8.3
- CNA · redhat
- 8.3
- agree
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
| Vendor | Product | CPE |
|---|---|---|
| redhat | shim | cpe:2.3:a:redhat:shim |
| redhat | enterprise linux | cpe:2.3:o:redhat:enterprise_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- redhat enterprise linux7.0
- 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.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | shim-aa64 | before 15.8-4.el8_9.alma.1 | 15.8-4.el8_9.alma.1 |
| AlmaLinux:8 | shim-ia32 | before 15.8-4.el8_9.alma.1 | 15.8-4.el8_9.alma.1 |
| AlmaLinux:8 | shim-x64 | before 15.8-4.el8_9.alma.1 | 15.8-4.el8_9.alma.1 |
| AlmaLinux:9 | shim-aa64 | before 15.8-4.el9_3.alma.1 | 15.8-4.el9_3.alma.1 |
| AlmaLinux:9 | shim-x64 | before 15.8-4.el9_3.alma.1 | 15.8-4.el9_3.alma.1 |
| Debian:10 | shim | before 15.8-1~deb10u1 | 15.8-1~deb10u1 |
| Debian:12 | shim | before 15.8-1~deb12u1 | 15.8-1~deb12u1 |
| Debian:13 | shim | before 15.8-1 | 15.8-1 |
| openSUSE:Leap Micro 5.3 | shim | before 15.8-150300.4.20.2 | 15.8-150300.4.20.2 |
| Red Hat:enterprise_linux:7::client | mokutil | before 0:15.8-1.el7 | 0:15.8-1.el7 |
| Red Hat:enterprise_linux:7::client | mokutil-debuginfo | before 0:15.8-1.el7 | 0:15.8-1.el7 |
| Red Hat:enterprise_linux:7::client | shim | before 0:15.8-3.el7 | 0:15.8-3.el7 |
| Red Hat:enterprise_linux:7::client | shim-ia32 | before 0:15.8-1.el7 | 0:15.8-1.el7 |
| Red Hat:enterprise_linux:7::client | shim-signed | before 0:15.8-1.el7 | 0:15.8-1.el7 |
| Red Hat:enterprise_linux:7::client | shim-unsigned-ia32 | before 0:15.8-3.el7 | 0:15.8-3.el7 |
| Red Hat:enterprise_linux:7::client | shim-unsigned-x64 | before 0:15.8-3.el7 | 0:15.8-3.el7 |
| Red Hat:enterprise_linux:7::client | shim-x64 | before 0:15.8-1.el7 | 0:15.8-1.el7 |
| Red Hat:enterprise_linux:8::baseos | shim | before 0:15.8-4.el8_9 | 0:15.8-4.el8_9 |
| Red Hat:enterprise_linux:8::baseos | shim-aa64 | before 0:15.8-4.el8_9 | 0:15.8-4.el8_9 |
| Red Hat:enterprise_linux:8::baseos | shim-ia32 | before 0:15.8-4.el8_9 | 0:15.8-4.el8_9 |
| Red Hat:enterprise_linux:8::baseos | shim-x64 | before 0:15.8-4.el8_9 | 0:15.8-4.el8_9 |
| Red Hat:enterprise_linux:9::baseos | shim | before 0:15.8-4.el9_3 | 0:15.8-4.el9_3 |
| Red Hat:enterprise_linux:9::baseos | shim-aa64 | before 0:15.8-4.el9_3 | 0:15.8-4.el9_3 |
| Red Hat:enterprise_linux:9::baseos | shim-x64 | before 0:15.8-4.el9_3 | 0:15.8-4.el9_3 |
+28
Same product
redhat: all recordsOther highest-scoring records for the same primary product.
- CVE-2014-3676Heap-based buffer overflow in Shim allows remote attackers to execute arbitrary code via a crafted IPv6 address, related to the "tftp:// DHC32Monitor
- CVE-2022-28737There's a possible overflow in handle_image() when shim tries to load and execute crafted EFI executables31Monitor
- CVE-2014-3677Unspecified vulnerability in Shim might allow attackers to execute arbitrary code via a crafted MOK list, which triggers memory corruption.31Monitor
Published before and after this one in the same product
- ← EarlierCVE-2014-3675Oct 22, 2014 · Shim allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted DHCPv6 packet.21Monitor
- Later →CVE-2023-40548Jan 29, 2024 · Shim: interger overflow leads to heap buffer overflow in verify_sbat_section on 32-bits systems29Monitor
- Later →CVE-2023-40546Jan 29, 2024 · Shim: out-of-bounds read printing error messages22Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| almalinux:shim-aa64 | 15.8-4.el8_9.alma.1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:shim-ia32 | 15.8-4.el8_9.alma.1 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:shim-x64 | 15.8-4.el8_9.alma.1 · AlmaLinux:8 | Package registry (OSV) |
| debian:shim | 15.8-1~deb12u1 · Debian:12 | Package registry (OSV) |
| opensuse:shim | 15.8-150300.4.20.2 · openSUSE:Leap Micro 5.3 | Package registry (OSV) |
| red hat:mokutil | 0:15.8-1.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:mokutil-debuginfo | 0:15.8-1.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:shim | 0:15.8-2.el8_2 · Red Hat:rhel_aus:8.2::baseos | Package registry (OSV) |
| red hat:shim-aa64 | 0:15.8-3.el9 · Red Hat:rhel_eus:9.0::baseos | Package registry (OSV) |
| red hat:shim-ia32 | 0:15.8-2.el8_2 · Red Hat:rhel_aus:8.2::baseos | Package registry (OSV) |
| red hat:shim-signed | 0:15.8-1.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:shim-unsigned-aarch64 | 0:15.8-2.el9 · Red Hat:rhel_eus:9.0::appstream | Package registry (OSV) |
| red hat:shim-unsigned-ia32 | 0:15.8-3.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:shim-unsigned-x64 | 0:15.8-2.el9 · Red Hat:rhel_eus:9.0::crb | Package registry (OSV) |
| red hat:shim-x64 | 0:15.8-2.el8_2 · Red Hat:rhel_aus:8.2::baseos | Package registry (OSV) |
| suse:pcr-oracle | 0.4.6-2.1 · SUSE:Linux Micro 6.0 | Package registry (OSV) |
| suse:shim | 15.8-150300.4.20.2 · SUSE:Linux Enterprise Micro 5.3 | Package 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.
No history yet (it accumulates with the daily EPSS job).
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.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2022-28737190 days apartThere's a possible overflow in handle_image() when shim tries to load and execute crafted EFI executables31Monitor
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 on the same network segment can trigger it.
- No account or password is required.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
Impact can extend beyond the vulnerable component (scope changes).
- Attack vector
- Adjacent
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-787 · Out-of-bounds WriteCVSS vector
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/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.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (12 more)Show less
- access.redhat.com/errata/RHSA-2024:1835
- access.redhat.com/errata/RHSA-2024:1873
- access.redhat.com/errata/RHSA-2024:1876
- access.redhat.com/errata/RHSA-2024:1883
- access.redhat.com/errata/RHSA-2024:1902
- access.redhat.com/errata/RHSA-2024:1903
- access.redhat.com/errata/RHSA-2024:1959
- access.redhat.com/errata/RHSA-2024:2086
- access.redhat.com/security/cve/CVE-2023-40547
- bugzilla.redhat.com/show_bug.cgi?id=2234589
- www.openwall.com/lists/oss-security/2024/01/26/1
- lists.debian.org/debian-lts-announce/2024/05/msg00009.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.