EDK II CVE-2024-38796: Azure Linux Attestation and Broader Scope

The integer‑overflow vulnerability tracked as CVE‑2024‑38796 in the EDK II PeCoffLoaderRelocateImage function is a real, medium‑severity memory‑corruption bug in widely reused UEFI/OVMF firmware code — and while Microsoft has publicly attested that Azure Linux includes the affected open‑source component, that attestation documents what Microsoft has validated so far and does not prove Azure Linux is the only Microsoft product that could include EDK II and therefore be in scope.

Background / Overview​

EDK II (the TianoCore reference implementation of UEFI) contains a heap/Integer‑overflow bug in the PE/COFF loader routine PeCoffLoaderRelocateImage that can lead to memory corruption when specially crafted relocation data is processed. Multiple vendors and distribution trackers (Debian, Ubuntu, Red Hat, Amazon Linux, and others) treated the issue as medium severity and issued patches for their edk2/ovmf packages; public vulnerability databases list the CVSS v3 score around 5.9. Microsoft’s public messaging for this and similar third‑party CVEs uses machine‑readable CSAF/VEX attestations to declare what the vendor’s product inventory has validated. For CVE‑2024‑38796 Microsoft stated that Azure Linux “includes this open‑source library and is therefore potentially affected,” and that Microsoft will update the CVE/VEX entries if additional Microsoft products are discovered to carry the same upstream component. That wording is an inventory attestation for the validated product set — not an exhaustive negation of impact elsewhere.

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What CVE‑2024‑38796 actually is​

Technical summary​

• The bug is an integer overflow / memory‑corruption issue in EDK II’s PeCoffLoaderRelocateImage (BasePeCoff.c) used to process relocation directory entries for PE/COFF images in UEFI environments.
• The problematic arithmetic around RelocDir->VirtualAddress and RelocDir->Size can overflow, producing incorrect size/offset calculations and enabling out‑of‑bounds memory access during relocation, which leads to corruption of memory and potentially crashes or other integrity failures.
• Upstream TianoCore acknowledged and published fixes; downstream Linux distributors (Debian/Red Hat/Ubuntu/Oracle/Amazon Linux, etc. have issued package updates for edk2/ovmf to include the upstream mitigation.

Exploitability and impact profile​

• The NVD/distributor scoring and vendor notes place CVSSv3 around 5.9 (medium). The attack vector is typically adjacent network (e.g., virtual machine firmware interfaces, hypervisor‑provided devices or virtual firmware images), not an unauthenticated remote web service. Realistic exploitation tends to require some level of access or the ability to supply crafted VM firmware or image inputs.
• Practical impacts range from local denial‑of‑service (firmware/VM instability) to integrity loss of a VM or guest if an attacker can feed crafted PE/COFF relocation data to the UEFI loader. There is no public, confirmed widespread RCE proof-of-concept tied to this CVE at publication time; the operational risk concentrates on virtualization and firmware image handling pipelines.

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Microsoft’s statement: what it means in practice​

Microsoft’s MSRC messaging and VEX/CSAF attestations are intentionally product‑scoped. When Microsoft says it has published a VEX/CSAF attestation that Azure Linux includes the vulnerable open‑source library, that signifies:

• Microsoft has completed an internal inventory and mapping exercise for the Azure Linux distribution and found edk2/OVMF artifacts there that include the vulnerable code, so Azure Linux has been marked as potentially affected in the attestation.
• Microsoft has committed to update the CVE and VEX/CSAF records if additional Microsoft products are found to include the same vulnerable upstream component. That is an operational promise to expand the published mapping as inventory work proceeds.

Crucially, this statement is procedural and time‑boxed: it reports what Microsoft has validated and attested to date, not a comprehensive sweep of all Microsoft SKUs, images, or partner‑provided artifacts.

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Is Azure Linux the only Microsoft product that includes EDK II and could be affected?​

Short answer: No — Azure Linux is the only Microsoft product Microsoft has publicly attested as including the affected EDK II components so far, but that does not mean no other Microsoft product can include or ship the same upstream code.
Longer explanation and reasoning:

• Inclusion of an upstream open‑source component is a per‑artifact, per‑build property. Whether a given Microsoft product (VM image, kernel, WSL2 kernel, curated container, marketplace image, DSVM, Azure ML appliance, or firmware bundle) contains a vulnerable edk2/ovmf artifact depends on how that artifact was built and packaged.
• Microsoft ships many artifacts that could plausibly incorporate EDK II or OVMF binaries:
• Azure Linux (explicitly attested).
• Marketplace images, DSVMs, and other Microsoft‑published virtual appliance images which can include OVMF/edk2 firmware in their VM templates.
• Container images and curated runtime artifacts used in Azure services when they contain firmware tooling or OVMF as part of guest tooling (less common, but possible).
• Third‑party marketplace images hosted in Azure: Microsoft’s attestation for Azure Linux does not automatically cover partner‑built appliances.
• Many Linux distributions that include edk2/ovmf (Debian, Ubuntu, Red Hat, Oracle, Amazon Linux) issued independent patches; this independent evidence shows the vulnerability exists in the upstream edk2 code and was widely present in several vendor packages, reinforcing that the footprint is broader than a single vendor product.

Therefore, while Microsoft’s public VEX/CSAF entry currently lists Azure Linux, customers should treat that as an authoritative, machine‑readable statement for Azure Linux only — and not as a definitive guarantee that no other Microsoft artifact in their environment includes the vulnerable EDK II build.

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Evidence: cross‑checking the claim with independent sources​

To validate the technical facts and scope, the following independent sources converge on the same core findings:

• TianoCore/EDK II upstream advisory and repository activity track the bug in PeCoffLoaderRelocateImage and show the upstream patch. Public advisories and the upstream issue/PR reveal the problematic arithmetic and the corrected checks. (TianoCore advisory / GitHub security advisory).
• Distribution advisories: Debian, Ubuntu, Red Hat, Oracle, and Amazon Linux all published edk2/ovmf package updates and security notices describing the same vulnerability and linking to upstream fixes. These independent vendor advisories confirm the bug and the remediation windows across multiple ecosystems.
• Public vulnerability aggregators (OSV, NVD, CVE catalogs) list CVE‑2024‑38796, summarize the vulnerability, and show the CVSS assessment and cross‑references — consolidating vendor and upstream data into a shared picture.
• Microsoft’s public attestation and VEX/CSAF practice is explained in the documents and analysis contained in the internal inventory summaries uploaded with the user files; these explain that Azure Linux is the first product Microsoft validated and that Microsoft will expand attestations to other products if further impact is found.

Taken together, the cross‑checks support three load‑bearing claims: the bug is in edk2 PeCoffLoaderRelocateImage; multiple distributors patched edk2/ovmf packages; and Microsoft’s VEX attestation currently names Azure Linux as the validated product, with a pledge to expand mapping if needed.

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Operational guidance for administrators and operators​

If you run Azure, on‑prem virtualization, or any service that creates/consumes VM firmware images, treat this CVE as actionable. The guidance below is pragmatic and prioritized.

Immediate triage (0–24 hours)​

• Inventory all images, VMs, and appliances that include or reference OVMF/edk2 firmware:
• Check VM templates, cloud images, and marketplace appliances used in your estate.
• For Linux distributions in VMs, check whether the distribution’s edk2/ovmf packages are present and their version.
• Prioritize public‑facing and multi‑tenant environments, CI build agents that produce VM images, and any image‑building pipelines that accept untrusted inputs.
• Monitor Microsoft’s VEX/CSAF feed for updates to the CVE mapping if you rely on Microsoft images; treat the Azure Linux attestation as authoritative for Azure Linux images published by Microsoft.

Verification commands and checks​

• On Linux images/VMs that may include edk2, check the edk2 or ovmf package version (dpkg/rpm queries or container image inspection).
• For OVMF/firmware used in virtualization: verify the OVMF/edk2 version in hypervisor/VM configuration and in the VM image artifact manifest.
• Where customers rely on marketplace images or partner appliances, request SBOMs or rebuild attestations from the image vendor if the image contains firmware components.

Remediation and mitigation (1–14 days)​

• Apply vendor edk2/ovmf package updates as provided by your distribution vendor (Debian, Ubuntu, Red Hat, Oracle, Amazon Linux, etc.. These vendors have released fixed package versions; apply their security updates to affected images and build pipelines.
• For immutable or signed image pipelines: rebuild the image using updated edk2/ovmf sources and reissue signed artifacts; do not rely solely on host OS package upgrades if the vulnerable firmware is included in the image payload.
• If you cannot patch immediately, reduce exposure by limiting methods that allow untrusted firmware or image ingestion, and isolate build infrastructure that can be used to inject crafted images.

Longer‑term controls (weeks → months)​

• Require SBOMs and rebuild attestations for any third‑party or marketplace images used in production.
• Add firmware/OVMF version checks to image‑release gating and CI pipelines to ensure vulnerable edk2 versions are not baked into artifacts.
• Where possible, limit the attack surface by restricting which agents or users can supply firmware blobs or custom VM images.

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Critical analysis — strengths and residual risks​

What Microsoft did well​

• Publishing CSAF/VEX attestations and starting with a clearly scoped product (Azure Linux) is operationally useful; it produces a machine‑readable signal Azure Linux customers can consume and automate against. That transparency accelerates triage for the attested product family.
• Microsoft’s explicit pledge to update CVE/VEX records if additional products are discovered is procedurally correct and creates a single authoritative channel for future changes.

Limitations and operational gaps to watch​

• The attestation covers only the product scope Microsoft has validated to date. Because edk2/ovmf is shipped and packaged by many vendors and may be embedded in numerous images, absence of an attestation does not equal absence of the vulnerable component in other Microsoft artifacts. Treat attestation absence as unresolved, not resolved.
• Statically‑built firmware or pre‑baked images will remain vulnerable until rebuilt with patched edk2 code. That rebuild inertia is the biggest remediation friction point in real deployments.
• Marketplace and partner images hosted in Azure may lag in their updates and are not automatically covered by Microsoft’s attestation unless explicitly mapped.

Unverifiable claims to be cautious about​

• It is not possible for external observers to exhaustively verify whether every Microsoft product or internal binary includes vulnerable edk2/ovmf code without Microsoft’s per‑product attestations, SBOMs, or signed rebuild attestations. Statements asserting "no other Microsoft products are affected" should be treated skeptically unless Microsoft publishes product‑level attestations or SBOMs that confirm absence.

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Practical checklist for WindowsForum readers and enterprises​

• Ingest Microsoft’s VEX/CSAF attestation data for Azure Linux and consume it in automated triage if you run Azure Linux images.
• Inventory all VM image build pipelines, marketplace images, and DSVM/curated images used by your teams. Tag any build pipelines that produce VM images for immediate review.
• For each candidate artifact:
• Determine if edk2 or OVMF is present.
• If present, confirm package/build version and whether the upstream fix is included.
• Patch or rebuild: apply vendor edk2 updates or rebuild images with patched EDK II sources; rotate signed images and redeploy.
• If you run Azure services that consume curated images (for example, Azure VM gallery or Marketplace appliances), ask the image publisher for SBOMs or attestations that they have rebuilt with the fixed edk2.
• Monitor VEX/CSAF feeds, distribution advisories, and your vendor patch channels for updated mappings and fixes.

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Conclusion — the clear, practical answer​

Microsoft’s MSRC statement that Azure Linux includes the open‑source EDK II code and is therefore potentially affected is accurate as an attestation of the product scope Microsoft has validated and published to date. However, that statement does not mean Azure Linux is the only Microsoft product that could contain the vulnerable EDK II/OVMF component. The vulnerability exists in upstream EDK II and has been patched by multiple distributors; any Microsoft artifact that embeds or ships the affected edk2/ovmf code (whether a marketplace image, firmware blob, or prebuilt appliance) could theoretically be in scope until Microsoft publishes a broader attestations map or the vendor provides explicit rebuild/SBOM attestations.
For operators: treat Microsoft’s Azure Linux attestation as an authoritative, product‑scoped automation input, but do not use it as a global all‑clear for other Microsoft images or appliances. Inventory, verify image/build artifacts, apply edk2/ovmf patches or rebuild images, and require SBOMs or rebuild attestations from image publishers to drive a defensible remediation program.

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Source: MSRC Security Update Guide - Microsoft Security Response Center