CVE-2026-42480: 
Linux Debian vulnerability analysis and mitigation

CVE-2026-42480 is a stack-based out-of-bounds read vulnerability in the VRML parser of Open CASCADE Technology (OCCT), specifically in the VrmlData_Scene::ReadLine function. It allows local attackers to cause a denial of service by supplying a crafted VRML file. Affected versions include OCCT ≤ 7.8.1 and pre-release builds up through V8.0.0-rc5 (including rc1–rc5, beta1, and master through commit c540f316). It was disclosed on April 30, 2026, and published to NVD on May 1, 2026. The vulnerability carries a CVSS v3.1 base score of 5.5 (Medium) (GitHub Advisory, Researcher Advisory).

The root cause is an out-of-bounds read (CWE-125) in VrmlData_Scene::ReadLine(), located in src/DataExchange/TKDEVRML/. The function declares a fixed-size stack buffer aBuffer[256] at line 328; the quoted-string escape handler increments an offset via ptr[++anOffset] without checking whether the offset remains within the buffer's bounds. Feeding the parser a VRML node with a line exceeding approximately 8,376 bytes causes the stack buffer to be overread at that offset, as confirmed by ASAN. This vulnerability is part of a broader set of six memory safety issues (CVE-2026-42476 through CVE-2026-42481) discovered by Feng Ning of Innora Security Research, all sharing the CWE-125 classification (Researcher Advisory, GitHub Advisory).

Successful exploitation causes a denial of service by crashing the application that processes the malicious VRML file. The vulnerability has no confidentiality or integrity impact — only availability is affected, as the out-of-bounds stack read leads to an abnormal program termination. Because exploitation requires local access and low privileges (e.g., the ability to supply a crafted file to an OCCT-based application), the blast radius is limited to the affected process and does not directly enable lateral movement or data exfiltration (GitHub Advisory, Researcher Advisory).

There is no evidence of in-the-wild exploitation or weaponized exploit kits at this time. A minimal proof-of-concept crash input (a 30,363-byte crafted VRML file) was published by the researcher and confirmed with ASAN at 100% reproducibility on OCCT 7.8.1 and master commit c540f316. The EPSS score is approximately 0.013–0.017%, placing it in the 4th percentile for exploitation likelihood. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog (Researcher Advisory, GitHub Advisory).

1. Craft a malicious VRML file: Create a VRML 2.0 file containing a node with a quoted string field whose line length exceeds 8,376 bytes, triggering the escape handler's unbounded offset increment in VrmlData_Scene::ReadLine().
2. Deliver the file: Place the crafted VRML file in a location accessible to the target application (e.g., a shared directory, upload endpoint, or local file path) that uses OCCT for 3D model parsing.
3. Trigger parsing: Cause the target OCCT-based application to open or import the crafted VRML file, invoking VrmlData_Scene::ReadLine() during parsing.
4. Achieve denial of service: The ptr[++anOffset] expression reads past the end of the 256-byte stack buffer aBuffer, causing an out-of-bounds memory access that crashes the application (Researcher Advisory).

• File System: Presence of unusually large VRML files (e.g., >8 KB with abnormally long single lines) in directories processed by OCCT-based applications; files with crafted quoted-string fields exceeding normal VRML syntax.
• Logs: Application crash logs or core dumps originating from processes invoking VrmlData_Scene::ReadLine; ASAN or sanitizer output referencing stack buffer overread at offset ~8376 in aBuffer[256].
• Process: Unexpected termination (segmentation fault or abort signal) of OCCT-based 3D modeling or CAD applications immediately after opening a VRML file (Researcher Advisory).

A patch was made available as of May 1, 2026; users should update OCCT to a version that includes bounds checking in the VrmlData_Scene::ReadLine quoted-string escape handler (capping anOffset at the buffer size before dereferencing). As a workaround, restrict or disable VRML file processing from untrusted sources, and validate/sanitize all VRML inputs before passing them to OCCT. Organizations using OCCT in CAD, simulation, or 3D visualization pipelines should prioritize upgrading, particularly if VRML import functionality is exposed to external users (GitHub Advisory, Researcher Advisory).

The vulnerability was reported by Feng Ning of Innora Security Research and disclosed on April 30, 2026, as part of a coordinated advisory covering six OCCT memory safety issues (CVE-2026-42476 through CVE-2026-42481). The GitHub Advisory Database classified it as Moderate severity. No significant vendor statements, broader media coverage, or notable community discussion beyond the initial researcher advisory have been identified at this time (Researcher Advisory, GitHub Advisory).