Security readout for executives and security teams
Plain-English summary
CVE-2023-40548 is a high-severity flaw in shim, software used during Linux secure boot. On 32-bit systems, a crafted PE binary can trigger memory corruption during boot. Business impact is mainly integrity and availability risk at a sensitive pre-OS stage, but exploitation is local and high complexity per CVSS.
Executive priority
Treat as a priority for Linux platform teams, not an internet-facing emergency. Patch during the next controlled maintenance window for affected systems, sooner for high-trust or regulated environments depending on boot-chain risk tolerance.
Technical view
Shim’s verify_sbat_section can integer-overflow while adding a user-controlled value parsed from a PE binary. The resulting allocation mismatch can cause a heap-based buffer overflow on 32-bit systems, leading to memory corruption, crash, or data integrity issues during boot. Red Hat lists affected shim, shim-signed, and shim-unsigned packages across RHEL 7, 8, and 9 streams.
Likely exposure
Exposure is most likely on affected Red Hat Enterprise Linux systems using listed shim packages, especially 32-bit boot paths. The bundle names RHEL 7, RHEL 8 variants, and RHEL 9 variants. Non-Red Hat exposure is not fully established here, though a Debian LTS reference exists.
Exploitation context
The CVSS vector is local, high complexity, no privileges, and no user interaction. The provided sources do not show CISA KEV listing or active exploitation. Abuse would target the boot process using a malicious PE binary, but no public exploitation status is confirmed in the supplied evidence.
Researcher notes
Evidence supports a 32-bit integer overflow leading to heap overflow in shim’s SBAT verification path. Red Hat provides multiple advisories, but the supplied bundle does not include fixed package version details. No KEV listing or active exploitation evidence is provided.
Mitigation direction
- Apply the relevant Red Hat shim security errata for affected RHEL versions.
- Prioritize systems relying on Secure Boot or sensitive boot-chain integrity.
- Check Red Hat CVE guidance for package-specific fixed versions and update requirements.
- For Debian or other distributions, consult the vendor advisory before assuming status.
Validation and detection
- Inventory installed shim, shim-signed, and shim-unsigned packages across Linux fleets.
- Compare package names and versions against the affected Red Hat entries.
- Confirm applicable RHSA updates are installed successfully.
- Review boot-chain change controls for systems where shim updates require operational coordination.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-190: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2023-40548 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H1.45.9redhatVulnerability scoring details
Base CVSS 3.1 score
7.4HighVector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- Source timelineredhat
Reported to Red Hat.
- Source timelineredhat
Made public.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- RHSA-2024:1834CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1835CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1873CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1876CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1883CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1902CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1903CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:1959CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- RHSA-2024:2086CVE reference, redhat · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/security/cve/CVE-2023-40548CVE reference, redhat · vdb-entry, x_refsource_REDHAT
- RHBZ#2241782CVE reference, redhat · issue-tracking, x_refsource_REDHAT
- https://lists.debian.org/debian-lts-announce/2024/05/msg00009.htmlCVE reference, CVE · x_transferred
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Integer Overflow or Wraparound
Integer Overflow or Wraparound represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.