CVE-2023-40547: Red Hat Enterprise Linux 7 · Out-of-bounds Write
Affects Red Hat Enterprise Linux 7Source CVE Database V5
Not known to be exploited · CVSS 8.3 High.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 5.4% chance of exploitation in 30 days – higher than 92% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 25 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 26 Oct 2026.
What to do
AI-suggested
- Secure the boot environment by restricting physical and network access to boot servers and infrastructure to prevent unauthorized interception or modification of boot traffic.
- Employ network-level protections such as strong encryption (e.g., HTTPS with validated certificates) and network segmentation to protect HTTP boot traffic from MitM attacks.
- Monitor and audit boot server configurations and logs for signs of compromise or unauthorized changes.
- Apply any available patches or updates from Red Hat addressing this vulnerability as soon as they are released.
- Consider upgrading to newer versions of Red Hat Enterprise Linux that may include improved secure boot mechanisms or mitigations.
- Implement hardware-based secure boot features and trusted platform modules (TPM) to enhance boot integrity verification.
- Use intrusion detection systems capable of monitoring early boot processes and network boot traffic anomalies.
- Educate system administrators on the risks of network booting and the importance of securing boot infrastructure.
- Regularly review and update incident response plans to include scenarios involving boot-level compromises.
Description
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.
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-2023-40547 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2234589 (opens in a new tab)
- openwall.com/lists/oss-security/2024/01/26/1 (opens in a new tab)
- lists.debian.org/debian-lts-announce/2024/05/msg00009.html (opens in a new tab)