Microsoft’s short public attestation that Azure Linux includes the implicated open‑source library is accurate and actionable for customers running Azure Linux images — but it is not a technical guarantee that no other Microsoft product could include the same vulnerable component.
CVE‑2024‑43204 is an Apache HTTP Server issue that can allow server‑side request forgery (SSRF) in specific configurations where mod_proxy is loaded and mod_headers is configured to alter the Content‑Type header using untrusted input. The Apache Project fixed the bug in Apache HTTP Server 2.4.64; upstream advisories and public vulnerability trackers recommend upgrading to 2.4.64 or later.
Microsoft’s Security Response Center (MSRC) published a concise product‑mapping statement for this CVE that reads, in effect: “Azure Linux includes this open‑source library and is therefore potentially affected by this vulnerability.” Microsoft also explains that it began publishing machine‑readable CSAF/VEX attestations starting with Azure Linux and will update the CVE if additional impacted Microsoft products are discovered. That wording is deliberate and important — it’s a product‑scoped attestation, not an exclusivity assurance.
Crucially, however, this attestation does not assert that Azure Linux is the only Microsoft product that could contain the same vulnerable open‑source code. Large vendors ship thousands of artifacts (VM images, Marketplace appliances, container base images, WSL kernels, SaaS components, telemetry agents, SDK packages and more). The presence of a package in one product family does not logically prove its absence from all others. Microsoft has explicitly framed its CSAV/VEX rollout as phased and has committed to updating CVE mappings when additional affected products are identified. Treat absence of a VEX attestation for a product as “not yet attested,” not “not affected.”
However, it is not an exclusivity guarantee. The practical, defensible posture for security teams is to treat MSRC’s attestation as the first high‑confidence signal and then perform artifact‑level discovery across other Microsoft-supplied images and components you run. Until Microsoft’s VEX coverage explicitly attests other products as Not Affected or Known Affected, absence of a product name in the MSRC advisory is not proof of cleanliness — it is absence of attestation, not evidence of absence.
Operationally: patch Azure Linux images now, upgrade Apache to 2.4.64+ where needed, and run a prioritized artifact sweep across Microsoft‑supplied images and partner Marketplace artifacts. Use SBOMs, image scanning, MSRC VEX feeds, and configuration checks (mod_proxy presence, mod_headers Content‑Type modifications) to reduce blind spots. These steps will move your estate from “unknown” to “known” much faster than waiting for vendor‑by‑vendor attestations alone.
CVE‑2024‑43204 is fixable; the operational work ahead is inventory, prioritized patching, and closing supply‑chain blind spots — Microsoft’s attestation helps for Azure Linux, but it doesn’t replace the artifact‑level verification every defender must run.
Source: MSRC Security Update Guide - Microsoft Security Response Center
Background / Overview
CVE‑2024‑43204 is an Apache HTTP Server issue that can allow server‑side request forgery (SSRF) in specific configurations where mod_proxy is loaded and mod_headers is configured to alter the Content‑Type header using untrusted input. The Apache Project fixed the bug in Apache HTTP Server 2.4.64; upstream advisories and public vulnerability trackers recommend upgrading to 2.4.64 or later.Microsoft’s Security Response Center (MSRC) published a concise product‑mapping statement for this CVE that reads, in effect: “Azure Linux includes this open‑source library and is therefore potentially affected by this vulnerability.” Microsoft also explains that it began publishing machine‑readable CSAF/VEX attestations starting with Azure Linux and will update the CVE if additional impacted Microsoft products are discovered. That wording is deliberate and important — it’s a product‑scoped attestation, not an exclusivity assurance.
What CVE‑2024‑43204 actually is — concise technical summary
- Affected software: Apache HTTP Server versions 2.4.0 through 2.4.63 (fixed in 2.4.64).
- Vulnerability class: Server‑Side Request Forgery (SSRF) triggered by a particular interaction between mod_proxy, mod_headers, and request-supplied values used to set Content‑Type.
- Trigger conditions required:
- Apache running a vulnerable 2.4.x release prior to 2.4.64.
- mod_proxy loaded and proxying to backends (the presence of mod_proxy is a core precondition).
- A configuration where mod_headers is instructed to set or modify the Content‑Type header using data that could be influenced by an HTTP request (an uncommon but feasible admin configuration).
- Practical impact: under the required configuration, a remote attacker who can reach the fronting proxy could coerce the server into making outbound requests to attacker‑controlled URLs (SSRF). Severity classifications across vendors range from Low to Moderate/High depending on the tracker, but the key operational point is the combination of version and configuration, not an automatic “all Apache installs are vulnerable.”
Parsing Microsoft’s statement: what “Azure Linux includes this open‑source library” really means
Microsoft’s MSRC line is an authoritative, narrowly scoped inventory result: Microsoft checked the build artifacts for Azure Linux (the Microsoft‑maintained Linux distribution often used as a base image in Azure) and found the upstream component that maps to the CVE. For Azure Linux customers, that attestation is a direct remediation signal — treat Azure Linux images as in‑scope and apply Microsoft’s patches.Crucially, however, this attestation does not assert that Azure Linux is the only Microsoft product that could contain the same vulnerable open‑source code. Large vendors ship thousands of artifacts (VM images, Marketplace appliances, container base images, WSL kernels, SaaS components, telemetry agents, SDK packages and more). The presence of a package in one product family does not logically prove its absence from all others. Microsoft has explicitly framed its CSAV/VEX rollout as phased and has committed to updating CVE mappings when additional affected products are identified. Treat absence of a VEX attestation for a product as “not yet attested,” not “not affected.”
Short, evidence-backed answer to the user’s question
- Is Azure Linux the only Microsoft product that includes the affected open‑source library and is therefore potentially affected?
- Short answer: No — Azure Linux is the only Microsoft product Microsoft has publicly attested so far to include the implicated component, but that attestation is product‑scoped and not a guarantee of exclusivity.
- Why that nuance matters: Microsoft’s wording gives a high‑confidence remediation target (Azure Linux) while also acknowledging the ongoing nature of software artifact inventories. Security teams that rely exclusively on the fact that only Azure Linux is named risk missing other Microsoft artifacts that may carry the same library until MSRC’s VEX mappings are expanded or until their own artifact scans confirm otherwise.
Where the vulnerable component could appear inside Microsoft’s ecosystem (practical inventory map)
Even if Microsoft’s attestation currently names only Azure Linux, here are the Microsoft artifact classes that can and do include third‑party open‑source libraries and therefore should be checked:- Azure Marketplace VM images and gallery images (many are built from or with Azure Linux components).
- Azure Kubernetes Service (AKS) node base images and custom node images used for clusters.
- Container base images published by Microsoft (for example, images that appear in Microsoft’s container registries or supply chains).
- VM images and appliances supplied via the Marketplace by Microsoft partners that may have been built from Linux distributions or include bundled runtimes (images can inherit vulnerable packages).
- WSL kernels and any Microsoft‑distributed Linux kernel or userland images embedded in Windows Subsystem for Linux offerings.
- Microsoft developer tooling and package managers (for example, artifacts produced by build tooling like vcpkg or reusable libraries that Microsoft maintains and publishes) — these can propagate libraries into other Microsoft products if used in builds.
- Managed platform runtimes (App Service runtime images, function app containers) where Microsoft supplies base images that customer apps run on. These images can include a vulnerable package depending on how they were built.
How to determine whether a Microsoft product you use is affected — pragmatic steps
Short, actionable checklist (prioritized):- Prioritize any workloads running Azure Linux images: patch or rebuild images to include the distribution security updates that map the Apache fix (upgrade to Apache 2.4.64+). Microsoft’s attestation makes these the highest‑confidence items to address.
- Inventory all Microsoft‑supplied images and artifacts you run (Marketplace images, official container images, App Service images, AKS node images, WSL distributions). Pull SBOMs where available. If MSRC VEX/CSAF data is available for the product, consume it programmatically.
- For each image or artifact, run these checks:
- Confirm Apache package version:
apachectl -vorhttpd -v, or query package managers (rpm -q httpd/dpkg -l | grep apache2). - Check loaded modules:
apachectl -M | grep proxyto verify whether mod_proxy is present. - Inspect vhost configuration for
ProxyPreserveHostand for any mod_headers directives that modify Content‑Type from request data. Search config files forProxyPreserveHostand forHeader set|append|edit Content-Type. - For containers/images: scan base layers and run
grep -R "httpd|apache2" /inside container shells or use image scanning tools that identify package versions. Rebuild images from patched base layers. - For Marketplace appliances and third‑party images: treat them as separate supply‑chain artifacts — ask vendors for an SBOM or VEX attestation, or perform your own image inspection.
Short‑term mitigations and configuration controls
- Upgrade to Apache HTTP Server 2.4.64 or later as the definitive fix. This is the only permanent resolution.
- If immediate upgrade is impossible, consider:
- Removing or disabling configuration rules that let mod_headers set Content‑Type from untrusted request input. Prefer explicit server‑side header definitions.
- Restricting access to the reverse proxy from untrusted networks (network ACLs, WAF rules, firewall rules) so that external attackers cannot reach the proxy vhosts that could trigger SSRF.
- For architectures where disabling mod_proxy is acceptable, temporarily disable mod_proxy for affected vhosts. Test thoroughly: disabling proxying can break legitimate functionality.
Why Microsoft’s VEX/CSAF rollout is a step forward — and where it leaves risk
Strengths of Microsoft’s approach- Publishing product‑level VEX/CSAF attestations makes automated triage feasible for enterprise defenders and reduces noisy alerts when a product is truly not affected. Microsoft’s blog explains the rationale and benefits for customers.
- Starting with Azure Linux is pragmatic: it’s a discrete, Microsoft‑managed distribution that appears in many Azure images, so covering it first yields broad benefit.
- The rollout is phased. Until a product is explicitly attested Not Affected or Known Affected via VEX/CSAF, customers must assume the product’s status is unverified. Relying solely on the absence of a VEX entry is risky for organizations running many Microsoft artifacts.
- Large vendors publish many artifacts: images, SDKs, agent packages, and partner appliances. Comprehensive artifact scanning and SBOM consumption remain essential defenses until attestation coverage is complete.
Practical examples: what defenders should do this week
- Run an image and package sweep for Apache across your estate. Use package queries and container image scanners. Prioritize any item that returns an Apache package version < 2.4.64.
- Flag any systems where mod_proxy is present and mod_headers directives alter Content‑Type from request inputs. Those are highest‑priority exposures.
- For Azure customers: prioritize Azure Linux VM images and marketplace images that explicitly cite the distribution; consume MSRC VEX feeds and any Microsoft security notifications about patched image releases.
- For third‑party or partner images in Marketplace: demand SBOMs or attestations, or stage the image and inspect packages before deployment.
Risk analysis — benefits, caveats, and residual exposure
Notable strengths- The upstream fix is available and widely packaged; the remediation path (upgrade to 2.4.64) is clear and practical. Apache’s advisory and multiple distribution trackers align on remediation guidance.
- Microsoft’s attestation and VEX publishing reduce uncertainty for the parts of their portfolio already covered, enabling automated triage and quicker patching cycles.
- Inventory blindness remains the real danger. Product‑level statements help, but supply‑chain complexity (containers, images, SDKs, partner artifacts) means many hidden copies of a vulnerable library can exist. Until those are located and remediated, risk persists.
- Phased attestation rollouts create windows where organizations may assume safety for a product because it’s not named, when in fact that product simply hasn’t been attested yet. Treat non‑attested products as “unknown” until proven otherwise.
Recommended, prioritized remediation checklist (clear, sequential)
- For any system running Apache, identify package version and modules immediately. If Apache < 2.4.64 and mod_proxy is present, escalate to “urgent.”
- Patch to Apache 2.4.64+ using your OS vendor’s security packages or rebuild from patched upstream if you manage custom builds. Verify service behavior post‑upgrade.
- If you run Azure Linux images, apply Microsoft’s updated images/patches first — MSRC’s attestation makes these the highest‑confidence place to start.
- For container images and Marketplace appliances: rebuild images from patched base layers and redeploy through CI/CD; if you can’t rebuild immediately, implement network restrictions and WAF rules to limit attacker reach.
- In parallel, gather SBOMs and query MSRC VEX/CSAF feeds programmatically for updates; treat VEX attestations as part of your automation pipeline but keep local verification checks in place.
Final assessment and conclusion
Microsoft’s MSRC messaging for CVE‑2024‑43204 — that Azure Linux includes the implicated open‑source component and is therefore potentially affected — is a precise, product‑scoped attestation that gives Azure Linux customers a clear action: inventory and patch their images. That statement is reliable and valuable.However, it is not an exclusivity guarantee. The practical, defensible posture for security teams is to treat MSRC’s attestation as the first high‑confidence signal and then perform artifact‑level discovery across other Microsoft-supplied images and components you run. Until Microsoft’s VEX coverage explicitly attests other products as Not Affected or Known Affected, absence of a product name in the MSRC advisory is not proof of cleanliness — it is absence of attestation, not evidence of absence.
Operationally: patch Azure Linux images now, upgrade Apache to 2.4.64+ where needed, and run a prioritized artifact sweep across Microsoft‑supplied images and partner Marketplace artifacts. Use SBOMs, image scanning, MSRC VEX feeds, and configuration checks (mod_proxy presence, mod_headers Content‑Type modifications) to reduce blind spots. These steps will move your estate from “unknown” to “known” much faster than waiting for vendor‑by‑vendor attestations alone.
CVE‑2024‑43204 is fixable; the operational work ahead is inventory, prioritized patching, and closing supply‑chain blind spots — Microsoft’s attestation helps for Azure Linux, but it doesn’t replace the artifact‑level verification every defender must run.
Source: MSRC Security Update Guide - Microsoft Security Response Center
