A critical memory‑safety flaw has been published affecting HDF5 version 1.14.6: CVE‑2025‑6270 is a heap‑based buffer overflow in the free‑space section lookup code, rooted in the function H5FS__sect_find_node inside H5FSsection.c, and public advisories and vulnerability trackers confirm a proof‑of‑concept exists and the issue is exploitable in practice under common deployment patterns.
HDF5 (Hierarchical Data Format 5) is a widely deployed binary container and C library used across scientific computing, engineering, and enterprise data pipelines to store large numerical arrays, chunked datasets and rich hierarchical metadata. Because HDF5 is frequently embedded directly into command‑line tools, language bindings (Python/R), container images, and server‑side ingestion services, memory‑safety defects in the core library can have broad operational impact when untrusted or malformed .h5 files are processed.
CVE‑2025‑6270 was publicly recorded on June 19, 2025; multiple national and distribution trackers (NVD, Ubuntu, SUSE and others) list the issue, describe the affected function and file, and classify the problem as a heap‑based buffer overflow that can be triggered by crafted HDF5 input.
Source: MSRC Security Update Guide - Microsoft Security Response Center
Background
HDF5 (Hierarchical Data Format 5) is a widely deployed binary container and C library used across scientific computing, engineering, and enterprise data pipelines to store large numerical arrays, chunked datasets and rich hierarchical metadata. Because HDF5 is frequently embedded directly into command‑line tools, language bindings (Python/R), container images, and server‑side ingestion services, memory‑safety defects in the core library can have broad operational impact when untrusted or malformed .h5 files are processed.CVE‑2025‑6270 was publicly recorded on June 19, 2025; multiple national and distribution trackers (NVD, Ubuntu, SUSE and others) list the issue, describe the affected function and file, and classify the problem as a heap‑based buffer overflow that can be triggered by crafted HDF5 input.
What the advisory says — concise summary
- Vulnerable component: HDF5 library up to and including 1.14.6.
- Faulty function: H5FS__sect_find_node in H5FSsection.c.
- Vulnerability class: heap‑based buffer overflow (CWE‑119 / CWE‑122).
- Attack vector: local file input by default; practically remote‑triggerable when a server or service accepts .h5 uploads and parses them on the server side.
- Immediate impact: Denial‑of‑Service (process crash) and heap corruption; remote code execution (RCE) is theoretically possible but depends on allocator and runtime conditions and has not been shown as universally trivial.
Technical anatomy: where and why it fails
The vulnerable code path
At a high level, the flaw occurs during free‑space section handling: HDF5 maintains on‑disk and in‑memory structures to track free blocks and section metadata. The routine H5FS__sect_find_node is responsible for locating or matching free‑space section nodes during certain serialization and cache operations. Under malformed or adversarial input, bounds calculations or per‑field length assumptions used by the routine can be incorrect or unvalidated, allowing byte‑wise writes to advance past the end of an allocated serialization buffer and corrupt heap memory. This results in a classic heap overflow.One‑byte overflows matter
Public technical analyses of HDF5 memory defects in the 1.14.6 window repeatedly show that even a single‑byte or small out‑of‑bounds write can be dangerous: that one byte may flip a size or metadata field used by the memory allocator, corrupt adjacent heap control structures, or otherwise produce exploitable conditions depending on allocator layout and surrounding allocations. Modern mitigations (ASLR, hardened allocators, RELRO, PIE, stack canaries) raise the bar for turning a heap overflow into stable RCE, but they do not make these bugs benign — availability and integrity impacts are immediate and reliable in many environments.Evidence and reproducibility
Tracker entries and upstream issue threads indicate that a proof‑of‑concept or reproducer exists for this issue: the initial disclosure contains sanitizer traces (AddressSanitizer) and reproduction instructions demonstrating a heap write past the buffer boundary when a crafted .h5 input exercises the affected routine. That PoC materially reduces the lead time for attackers and penetration testers to weaponize the defect in unpatched systems.Exploitability and real‑world risk
Attack model
- The attacker provides a specially crafted .h5 file that contains corrupted free‑space section data or malformed length/offset fields.
- The vulnerable process (desktop app, batch tool, or server‑side ingestion service) opens or processes that file using a vulnerable HDF5 1.14.6 library.
- The HDF5 code path runs H5FS__sect_find_node, which performs unchecked byte‑wise serialization or buffer writes and produces a heap overflow.
- Depending on environment, the overflow causes an immediate crash (DoS) or — under favorable allocator and memory layout conditions, possibly with other primitives available — could be developed into more serious memory‑corruption exploitation.
Likely impacts (practical)
- Denial‑of‑Service: guaranteed and reproducible in many tested environments — the single most immediate operational risk.
- Data integrity loss: heap corruption can lead to silent file or process state corruption in long‑running services, especially when worker processes persist state after malformed input handling.
- Confidentiality: less likely from this specific overflow (public traces emphasize write‑past symptoms rather than controlled reads), but not impossible when combined with other flaws.
- Remote code execution (RCE): speculative — turning this primitive into reliable RCE depends on allocator behavior, presence of information leaks, and platform hardening. No broadly‑trusted public writeup demonstrates trivial RCE from CVE‑2025‑6270 at the time of disclosure. Treat RCE claims as unverified until reproducible by multiple independent researchers.
Attack surface amplification
Although the CVE is formally classified with a local attack vector, real‑world server configurations make it effectively remote in many scenarios. Any service that automatically accepts uploaded .h5 files (preview generation, metadata extraction, automated conversion, scientific ingestion pipelines, cloud processing tasks) can be triggered remotely by an unauthenticated file upload and thus elevates the risk profile significantly. Several prior HDF5 defects followed this pattern, and public advisories repeatedly flag server‑side ingestion as the highest‑risk deployment model.Where CVE‑2025‑6270 shows up: affected products and packaging
- Upstream affected: HDF5 ≤ 1.14.6 (canonical affected release cited across multiple trackers).
- Downstream: any binary, container image, or language binding (Python wheels, conda packages, R binaries) that bundles or links to HDF5 1.14.6 is potentially vulnerable — static linking increases remediation complexity because it requires rebuild or replacement of the consumer binary.
Vendor and distribution responses
- Official upstream (HDF Group) activity: trackers and distribution advisories reference upstream issue threads and pull requests that add defensive checks and bounds validation to related free‑space and serialization code; packagers must confirm that the specific upstream commits addressing H5FS__sect_find_node are present in their builds. Historically, HDF5 fixes in this release family have been applied as small, surgical commits rather than large consolidated advisories, so downstream packagers may map fixes differently.
- Distribution packaging: Ubuntu has assigned the CVE a medium priority and listed packages requiring evaluation, while SUSE marks the issue as resolved in their tree after applying backports; availability of vendor packages varies by distribution and release. Operators should check their distribution security tracker and package changelogs to confirm whether a shipped hdf5 package contains the upstream fix/commit SHA.
- Third‑party scanners: Snyk and other vulnerability services have published entries for CVE‑2025‑6270. At the time of disclosure Snyk reported no fixed version available from the HDF5 project (operators are advised to prefer vendor packages or to rebuild from upstream commits where needed).
Confirming remediation: what to look for when validating patches
When a vendor or package claims to have fixed CVE‑2025‑6270, operators should validate remediation using concrete indicators, not just package version numbers:- Confirm the hdf5 package changelog or vendor advisory lists the specific upstream commit SHA or pull request that addresses H5FS serialization and the H5FS__sect_find_node code path. HDF5 fixes have typically been traced to specific commits; packaging that lacks the commit is not equivalent to being patched.
- Prefer vendor or upstream releases that explicitly mention the CVE or the fix commits (for example a point release >1.14.6 that bundles the corrections). If no vendor package exists, consider building HDF5 from source with the corrective commits merged and then rebuilding any statically linked binaries that include it.
- Test patched binaries by re‑running the upstream PoC in a controlled, isolated environment (sandboxed with resource limits) to confirm the crash no longer occurs. Do not run untrusted PoC inputs on production hosts.
Immediate mitigation and incident response playbook
When you cannot patch immediately, deploy layered mitigations to reduce exposure and blast radius.Short‑term (first 24–72 hours)
- Inventory: Identify all hosts, containers, and images that ship HDF5 (system packages, Python wheels, conda packages, Docker images). Prioritize publicly accessible ingestion or preview services.
- Block or quarantine untrusted .h5 uploads: Replace automatic processing with manual review, or enforce a quarantine path that scans and validates files before decoding.
- Isolate and sandbox: Run any HDF5 processing in dedicated, least‑privilege containers with seccomp/AppArmor/SELinux profiles, memory and CPU limits, and restricted network access. Separate preview/metadata extraction into its own service so crashes are compartmentalized.
Medium‑term (within a patch window)
- Patch or rebuild: Apply vendor packages that include the upstream fix, or rebuild HDF5 from upstream commits that close the issue and redeploy statically linked artifacts. Validate with regression tests.
- Hardening: Ensure processes are built and deployed with modern exploit mitigations enabled (ASLR, PIE, RELRO, stack canaries). While these do not fix the bug, they materially increase exploitation difficulty.
- Monitoring and detection: Add detection rules to capture process crashes, sanitizer logs, and anomalous file‑handling errors. Hunt for unusual ingestion activity and scan logs for repeated hdf5‑related crashes.
Longer‑term
- Supply‑chain hygiene: Audit third‑party binaries, wheels and container images to find embedded HDF5 binaries; ask vendors to provide SBOMs and commit SHAs for the HDF5 code they include. Replace or rebuild images that embed vulnerable libraries.
- Adopt robust file‑parsing patterns: Where possible, parse untrusted files in memory‑safe wrappers or isolate parsing using language sandboxes or dedicated microservices running reduced privileges. Consider fuzzing critical file‑handling code as part of CI to detect regressions.
Practical checklist for Windows and Linux admins
- Search your inventory for hdf5 package versions and for binaries that statically link HDF5 (h5dump, h5ls, vendor tools).
- For Linux package managers: check Ubuntu, Debian, SUSE and your distro’s security tracker for explicit package updates referencing CVE‑2025‑6270. Do not assume upstream release numbers alone; confirm commit SHAs.
- For Windows/embedded appliances: verify vendor advisories or request a rebuild from your vendor if the product bundles HDF5. Reimaging or updating appliances may be required where static linkage prevents simple patching.
- For cloud images and containers: scan images for HDF5 artifacts, rebuild images from patched base layers, and avoid pulling untrusted images that may bundle 1.14.6.
Why this matters: ecosystem reach and past patterns
HDF5 is not a niche library; it underpins HPC workflows, scientific tools, data science stacks and automated conversion pipelines. Vulnerabilities clustered around a single release (1.14.6) across multiple serialization and memory‑handling routines increase the operational risk: even if a single CVE is patched, other related issues in the same release family may remain until a consolidated point release is made and adopted. Historically, multiple HDF5 defects in the 1.14.6 timeframe were disclosed and tracked as separate CVEs, each affecting different helpers (serialization, VM helpers, object header encoding). That history underscores the importance of comprehensive remediation and supply‑chain verification rather than one‑off fixes.Risk assessment and final verdict
CVE‑2025‑6270 is a practical vulnerability: the flaw is specific, reproducible with sanitizer evidence, and PoC material exists in the wild. The primary immediate impact is denial‑of‑service and heap corruption, which is of high concern for automated ingestion services and long‑running processing pipelines. While reliable RCE remains unproven publically for this CVE, the presence of a heap overflow in a widely linked library is a high‑value primitive for attackers and should be remediated without delay in exposed environments. Cross‑checking NVD, Ubuntu and third‑party trackers confirms the vulnerability details and disclosure timeline; distribution packaging and vendor fixes vary, so operators must validate that the specific fix commits are included in their deployed builds.Quick reference — what to do now
- Inventory all HDF5 uses and prioritize public ingestion endpoints.
- Apply vendor updates that explicitly reference the CVE or upstream fix commits; if none exist, rebuild from upstream with the corrective commits merged.
- Quarantine automatic processing of untrusted .h5 files until hosts are validated or patched.
- Harden parsing services (sandboxing, cgroups, ulimits) and monitor for crashes.
Conclusion
CVE‑2025‑6270 is another in a string of HDF5 memory‑safety defects disclosed against the 1.14.6 release line. The vulnerability in H5FS__sect_find_node (file H5FSsection.c) produces a heap‑based buffer overflow that is reproducible with the public PoC and poses a credible operational threat — especially to services that automatically parse untrusted .h5 files. Administrators should treat the issue as urgent for exposed ingestion services: inventory, contain, apply vendor patches or rebuild from upstream commits, and harden parsing workloads immediately. Cross‑checks against NVD, Ubuntu, SUSE and third‑party vulnerability services confirm the technical facts, the public PoC status, and the practical remediation steps that defenders should follow.Source: MSRC Security Update Guide - Microsoft Security Response Center
