Calling any of Go's Parse* functions on specially crafted, deeply nested source can exhaust the stack and trigger a panic — a vulnerability tracked as CVE-2024-34155 that sits in the go/parser standard library and has been fixed in the Go 1.22.7 and 1.23.1 releases; Microsoft’s public vulnerability note identifies the Azure Linux distribution as a known carrier of the implicated open‑source library, but that attestation is a scoped inventory statement — not a guarantee that no other Microsoft product can ship the same vulnerable component.
CVE-2024-34155 is a stack exhaustion vulnerability in the Go standard library’s parser package (go/parser). The defect arises when parsing Go source that contains deeply nested literals; the parser’s recursion depth can grow without bound, exhausting the native stack and causing the process to panic. The Go team assigned the vulnerability GO-2024-3105 and shipped fixes in the minor Go point releases go1.22.7 and go1.23.1. Authoritative vulnerability databases and the Go project changelogs reflect the same details and fixed release versions.
This is primarily an availability risk: a remote or local attacker who can cause a vulnerable binary to parse attacker-controlled Go source (or other inputs that reach the parser APIs) can provoke a panic and denial of service. The bug is not a memory corruption or data‑exfiltration primitive; its operational impact is blunt but real for systems that accept untrusted Go source or parse code-like inputs. Several independent vulnerability databases (NVD, OSV, vendor advisories) catalog the same facts and link to the Go issue and the upstream code change.
Crucially, that wording is not a categorical exclusivity claim. A product-level attestation named in an MSRC record marks “what Microsoft has checked and published so far,” not “what Microsoft has checked everywhere.” Multiple independent analyses of Microsoft’s VEX/CSAF rollout underscore the same point: Azure Linux was the first Microsoft product to receive these machine-readable attestations, and the wording explicitly leaves room for future mappings if other Microsoft artifacts are found to include the same third‑party component. In short: Azure Linux is the only Microsoft product Microsoft has publicly attested to include this component so far, but nothing in the attestation technically proves other Microsoft products cannot carry the vulnerable Go code.
Source: MSRC Security Update Guide - Microsoft Security Response Center
Background
CVE-2024-34155 is a stack exhaustion vulnerability in the Go standard library’s parser package (go/parser). The defect arises when parsing Go source that contains deeply nested literals; the parser’s recursion depth can grow without bound, exhausting the native stack and causing the process to panic. The Go team assigned the vulnerability GO-2024-3105 and shipped fixes in the minor Go point releases go1.22.7 and go1.23.1. Authoritative vulnerability databases and the Go project changelogs reflect the same details and fixed release versions.This is primarily an availability risk: a remote or local attacker who can cause a vulnerable binary to parse attacker-controlled Go source (or other inputs that reach the parser APIs) can provoke a panic and denial of service. The bug is not a memory corruption or data‑exfiltration primitive; its operational impact is blunt but real for systems that accept untrusted Go source or parse code-like inputs. Several independent vulnerability databases (NVD, OSV, vendor advisories) catalog the same facts and link to the Go issue and the upstream code change.
What CVE-2024-34155 actually affects
The technical footprint
- Affected component: Go standard library package go/parser.
- Affected symbols/paths: the underlying parsing routines (parser.parseLiteralValue) and the exported Parse* functions such as ParseDir, ParseExpr, ParseExprFrom, and ParseFile, which derive from that internal logic.
- Affected Go toolchain ranges: versions before go1.22.7, and go1.23.0 up to (but not including) go1.23.1. In short, upgrade to go1.22.7 or go1.23.1 (or later) to obtain upstream fixes.
Exploitability and scope
- Attack complexity is moderate: the vulnerability requires feeding deeply nested literal structures into a parser path that the target binary actually invokes. Not every Go application uses or exposes go/parser APIs; many applications simply use compiled packages and do not parse Go source at runtime. That said, tools and services that do parse Go source (linters, formatters, code analysis tools, build tools, some CI/CD components, language servers, custom plugins, REPL-like services, and code execution sandboxes) are logically in scope. Vulnerable applications that parse untrusted source data are the primary concern. Independent vulnerability trackers and vendor advisories consistently describe the functional impact as a DoS/panic risk.
Microsoft’s MSRC statement: what it says — and what it doesn’t
When Microsoft’s security update guide or MSRC entry notes that “Azure Linux includes this open‑source library and is therefore potentially affected,” that phrasing is an inventory attestation for the Azure Linux product family: Microsoft has completed a mapping step that shows Azure Linux images include the vulnerable upstream code and therefore require attention. Microsoft has publicly committed to extending machine‑readable CSAF/VEX attestations beyond Azure Linux in a phased manner; as that rollout proceeds, additional Microsoft product mappings will be published if inventories show the component is present elsewhere.Crucially, that wording is not a categorical exclusivity claim. A product-level attestation named in an MSRC record marks “what Microsoft has checked and published so far,” not “what Microsoft has checked everywhere.” Multiple independent analyses of Microsoft’s VEX/CSAF rollout underscore the same point: Azure Linux was the first Microsoft product to receive these machine-readable attestations, and the wording explicitly leaves room for future mappings if other Microsoft artifacts are found to include the same third‑party component. In short: Azure Linux is the only Microsoft product Microsoft has publicly attested to include this component so far, but nothing in the attestation technically proves other Microsoft products cannot carry the vulnerable Go code.
Could other Microsoft products be affected?
Short answer: yes, potentially — but it depends on whether a product ships or embeds a vulnerable Go runtime or binaries built with a vulnerable Go toolchain.How other Microsoft products might become carriers
- Microsoft products or services that embed Go-built binaries will carry the standard library code inside those binaries. If the binary was built with a vulnerable Go toolchain (e.g., go1.23.0 or earlier than a fixed point), the runtime and possibly the parser package will be present in the produced executable. Examples of Microsoft-maintained Go code include the Azure SDK for Go, many cloud-native agents and controllers, and Microsoft-owned open source projects hosted on GitHub that are written in Go. The Azure SDK for Go is an official Microsoft repository and ecosystem actively maintained by Microsoft; GitHub’s official CLI and other GitHub CLI-related tooling are Go projects maintained under GitHub’s organization (GitHub is part of Microsoft). These are representative examples showing that Microsoft both produces and distributes Go-based software.
- Container images, CI/CD runners, build agents, cloud-native controllers, or managed service appliances that include a Go toolchain (or include Go CLI binaries that themselves embed the standard library) can be carriers. Any Microsoft-managed container image that bundles a Go runtime or that contains Go-built tools needs inventory checks to confirm it was built with a patched toolchain.
Why the MSRC attestation doesn’t equal “all clear” for other products
- Microsoft’s VEX/CSAF rollout started with Azure Linux as the canonical, well-scoped first product. The MSRC statement is both accurate and conservative: it tells Azure Linux users to act and promises to expand mappings for other Microsoft products once the internal inventory work is completed. It does not mean that other products are confirmed safe. Multiple internal and external analysts have made this same distinction: the attestation signals what Microsoft has validated and published, not the entirety of Microsoft’s product landscape. Treat un‑attested Microsoft artifacts as potentially affected until verified.
Practical detection, verification, and mitigation steps
If you manage Microsoft‑owned images, services, or third‑party artifacts that run on Microsoft platforms, follow a disciplined approach: inventory → detect → patch → verify. Below are actionable technical steps defenders and maintainers can use.1. Inventory first (what to look for)
- Identify services, images, or binaries that:
- Call any go/parser Parse* APIs at runtime.
- Ship with an embedded Go runtime (i.e., were produced by the Go toolchain).
- Contain language servers, linters, formatters, or developer tools that parse Go source.
- Candidate Microsoft artifacts to prioritize for inventory: Azure SDK for Go packages and downstream binaries, GitHub/GitHub‑owned CLI tools, Microsoft-maintained container images that include Go-built tooling, and any cloud agents or operators that are known to be implemented in Go. Confirm the presence of Go code with a repository or package scan.
2. Detect — confirm whether a binary was built with a vulnerable Go toolchain
- Use the Go tooling and binary inspection to check build metadata:
- Run
go version -m <binary>on Linux/Windows builds (where available) to extract the embedded Go toolchain version and module metadata. - Alternatively, programmatically use the Go debug/buildinfo APIs or a small helper that uses debug/buildinfo.ReadFile to read the Go version and module info embedded in a binary.
- Note limitations:
- Some builds (for example,
go buildwithout module metadata or when build information has been stripped) can omit clear module version strings; in those cases,strings <binary> | grep 'go1.'or other heuristics may help, but they are less reliable. Vulnerability scanners sometimes miss Go runtime versions for precisely this reason.
3. Patch — update the Go toolchain and rebuild or apply vendor patches
- For components you build and control:
- Upgrade the Go toolchain used for builds to go1.22.7 or go1.23.1 (or any later release that includes the fixes).
- Rebuild all Go binaries and images so they incorporate the patched standard library.
- For third‑party binaries or vendor artifacts:
- Require vendors to confirm the Go toolchain version used to produce their binaries.
- If vendor-supplied artifacts are not rebuildable by you, seek updated releases from the vendor or refrain from running untrusted parsing features until mitigated.
4. Compensating controls (if you cannot immediately rebuild)
- Block or limit any feature paths that accept untrusted Go source or code for parsing at runtime.
- Introduce input size and nesting depth limits at the application boundary; for example, reject inputs with excessive nesting or extremely long token sequences that could exhaust recursion limits.
- Run potentially dangerous parsing operations in isolated, constrained sandboxes with limited memory and CPU quotas (cgroups, containers, VMs) to reduce the blast radius of a panic or resource exhaustion.
5. Verify & harden
- After rebuilding with a patched toolchain, test parsing flows with stress inputs or fuzzing harnesses that target deeply nested literal structures to validate the fix and to confirm no regressions.
- Use static and runtime vulnerability scanning tools (govulncheck, OSV scanners, and binary build‑info checks) as part of CI/CD to prevent reintroduction.
Detection and auditing guidance for Microsoft customers and defenders
- If you run Azure Linux images: follow Microsoft’s published VEX/CSAF guidance for the product-level mapping; Azure Linux images are known to include the implicated library and will receive distribution updates as Microsoft rolls fixes into the distro. MSRC has published that Azure Linux includes the library and is potentially affected, and will update VEX/CSAF records if further Microsoft products are identified as carriers. That message is both a prompt to patch and a commitment to transparency.
- If you rely on Microsoft‑supplied SDKs, CLIs, or GitHub-hosted tooling: inventory the versions of the tools you ship or consume. The Azure SDK for Go and many GitHub CLI components are Go-based, which means that binaries or artifacts produced by those projects may include the standard library at runtime. If you consume prebuilt binaries from Microsoft or GitHub, request or verify the toolchain version used to build those binaries.
- For large enterprises with many artifacts: automate binary scanning in your pipeline using
go version -m,go tool buildid, or vendor-provided build metadata. Where version metadata is missing, apply heuristics (strings checks, provenance records) and prioritize human review for high-risk services (code parsers, build servers, language servers).
Strengths and risks in Microsoft’s attestation approach — critical analysis
osoft’s rollout of machine‑readable CSAF/VEX attestations and its decision to start with Azure Linux is a positive step for supply‑chain transparency. Publishing structured attestations reduces ambiguity for customers and enables automated triage by security tooling. The MSRC blog describing the VEX rollout clarifies the intended phased approach and the limited initial scope. This is an operational and policy improvement that benefits defenders.- The attestation’s conservative wording — naming only the product Microsoft has inventoried and promising updates when additional products are found to contain the component — is truthful and avoids overclaiming. It provides customers an authoritative place to start remediation actions rather than leaving them to guess where the component may be present.
Risks and limitations
- The attestation is product-scoped, not ecosystem‑scoped. That means Microsoft customers should not assume that an attestation naming Azure Linux implies no other Microsoft artifacts are affected. In practice, large vendors and cloud providers ship thousands of artifacts; inventory work is nontrivial and can lag disclosure timelines. Analysts and practitioners have repeatedly warned that Azure Linux attestation is an initial mapping, not the end of the story. Treat un‑attested artifacts as “unknown until proven safe.”
- Machine‑readable attestations are only useful if they are complete and kept current. The phased rollout is a pragmatic approach, but it raises the risk of false comfort for organizations that equate a single attestation with comprehensive coverage. Until Microsoft’s VEX/CSAF outputs cover the full product portfolio (or until customers run independent inventories), defenders must perform their own checks.
- Practical detection gaps exist for Go-built binaries: build metadata can be absent, stripped, or inconsistent (for example, when
go buildis used in certain ways). This can blind vulnerability scanners and slow remediation. Defenders must account for these blind spots with complementary approaches.
Recommended, prioritized action checklist (for platform owners and defenders)
- Inventory: run a focused scan for Go-built binaries and any code that calls go/parser or similar parsing APIs. Tag items by their business criticality.
- Confirm: use
go version -mor debug/buildinfo to read embedded Go toolchain version metadata in each binary. For images, inspect the image layers and package lists to find Go packages and toolchains. - Rebuild: for in‑house code, upgrade to go1.22.7 / go1.23.1 or later and rebuild every Go artifact. Treat this as a mandatory CI step for all Go-based build pipelines.
- Patch: if you maintain or ship Azure Linux images, apply the distribution updates Microsoft publishes; if you consume Microsoft artifacts, request vendor attestations and updated builds if you lack evidence of a patched toolchain.
- Mitigate: for workloads that parse untrusted source and cannot be immediately rebuilt, implement input validation limits, sandbox parsing operations, and add monitoring for unexpected panics.
- Verify: fuzz the parsing paths where feasible against deeply nested literals to ensure the fix is effective and to find regressions.
- Automate: incorporate binary metadata checks and govulncheck (or equivalent) into CI/CD to prevent regressions and to catch embedded vulnerabilities early.
Final assessment — what to tell your stakeholders
- Microsoft’s public statement that “Azure Linux includes this open‑source library and is therefore potentially affected” is accurate for the Azure Linux product family and is an important, actionable attestation for customers who run those images. Microsoft has also committed to expanding its CSAF/VEX mappings over time and to update CVE records if other products are identified.
- However, do not interpret that statement as a guarantee that no other Microsoft product includes the vulnerable go/parser code. Any Microsoft product, service, or image that ships a Go runtime or Go-built binaries compiled with an affected Go toolchain could, in principle, be affected. The responsible posture is to treat un‑attested Microsoft artifacts as potentially affected until inventory verification and rebuilds have been completed. Multiple community analyses and vendor-advisor commentary reach the same conclusion.
- Operationally, the immediate defensive imperative is straightforward: identify parsing‑exposed services and Go-built binaries in your estate, confirm their build toolchain versions, and rebuild packages with patched Go releases (go1.22.7 or go1.23.1+) to eliminate the vulnerable parser from production images and services. Use sandboxing and input limits as temporary mitigations where rebuilding is not immediately possible.
Conclusion
CVE-2024-34155 is a practical denial‑of‑service vulnerability in Go’s parser that the Go project fixed in the go1.22.7 and go1.23.1 releases. Microsoft’s MSRC attestation that Azure Linux includes the implicated library is both truthful and useful — it flags a Microsoft‑distributed product that has been inventory‑checked and needs attention — but it is not an exclusivity statement. Any Microsoft product that ships a vulnerable Go runtime or binaries built with an affected Go toolchain could be a carrier until explicitly checked and remediated. Defenders should treat the MSRC attestation as a starting point, not a finish line: run a proactive inventory, confirm build metadata, rebuild with patched toolchains, and apply sandboxing and input limits where immediate rebuilds are not feasible. The combination of Microsoft’s transparency via VEX/CSAF and disciplined, automated internal controls is the right strategy to manage the operational risk from this and similar open‑source supply chain exposures.Source: MSRC Security Update Guide - Microsoft Security Response Center
