CVE-2023-40548: Red Hat Enterprise Linux 7 · Out-of-bounds Write
Affects Red Hat Enterprise Linux 7Source CVE Database V5
Not known to be exploited · CVSS 7.4 High.
Data as of 25 Oct 2026, 19:02 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 37% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 29 Jan 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
AI-suggested
1. Apply official patches from Red Hat as soon as they become available to address the buffer overflow in Shim. 2. Restrict physical and local access to systems running 32-bit RHEL 7 to trusted personnel only, reducing the risk of local exploitation. 3. Implement strict boot media controls and secure boot policies to prevent unauthorized or malicious PE binaries from being loaded during the boot process. 4. Where possible, migrate from 32-bit to 64-bit architectures and upgrade to supported Red Hat Enterprise Linux versions to reduce exposure to legacy vulnerabilities. 5. Employ runtime integrity verification tools that monitor bootloader and kernel integrity to detect anomalies caused by exploitation attempts. 6. Conduct regular audits of boot configurations and verify the authenticity of boot components to ensure no tampering has occurred. 7. Use hardware-based security features such as TPM and UEFI Secure Boot with strict enforcement to mitigate unauthorized boot modifications. 8. Develop incident response plans that include boot-level compromise scenarios to quickly isolate and remediate affected systems.
Description
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.
References
- access.redhat.com/errata/RHSA-2024:1834 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1835 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1873 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1876 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1883 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1902 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1903 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:1959 (opens in a new tab)
- access.redhat.com/errata/RHSA-2024:2086 (opens in a new tab)
- access.redhat.com/security/cve/CVE-2023-40548 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2241782 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2024/05/msg00009.html (opens in a new tab)