CVE-2026-59181

Executive Summary

CVE-2026-59181 is a stack-based buffer overflow (CWE-121) in OpenImageIO's Cineon image file reader. A crafted Cineon file can specify a numberOfElements value exceeding the format maximum of eight, which CineonInput::open() uses as an unchecked loop bound while populating the fixed strings[8] array — writing pointers beyond the stack buffer and corrupting adjacent memory. The vulnerability is rated CVSS 3.1 score 6.1 (Medium), with High impact on Availability, Low on Integrity, and no Confidentiality impact; patches are available in versions 3.0.20.0, 3.1.15.0, and 3.2.0.3-beta1, but no public PoC or exploit code has been observed.

Technical Analysis

OpenImageIO is a widely used toolset for reading, writing, and manipulating image files, particularly in VFX and animation pipelines. The Cineon file format — a legacy Kodak format for film scanning — is parsed by CineonInput::open(), implemented in src/cineon.imageio/cineoninput.cpp.

The vulnerability arises from a validation gap in the Cineon header parsing logic:

• The Cineon header is expected to contain a maximum of eight image-channel/element descriptors (the fixed strings[8] array).
• A crafted file can supply a numberOfElements field with a value greater than eight.
• CineonInput::open() uses this attacker-controlled numberOfElements value directly as the loop bound when filling strings[8].
• Because the bound is unchecked, the loop writes pointers past the end of the fixed 8-element stack array and into adjacent stack state.

This is a classic CWE-121 (Stack-based Buffer Overflow) with a stack-buffer-overflow-out-of-bounds write primitive. The write is pointer-sized; the primary observable outcome described is memory corruption and denial of service. The CVSS subscores reflect this: I:L (Low Integrity — corrupted in-memory state) and A:H (High Availability — process crash/DoS), with C:N (no Confidentiality impact), consistent with a non-controlled, availability-focused corruption primitive rather than a demonstrated code-execution primitive.

Exploitation requires user interaction (UI:R) and is local (AV:L), meaning the attacker must deliver the malicious Cineon file to a victim, who must open or process it with an application built against a vulnerable OpenImageIO version. This is the typical file-parser attack surface for image-processing libraries used in rendering, compositing, and asset-management tools.

The CVSS vector reflects only the demonstrated impact. Out-of-bounds pointer writes on the stack are potentially exploitable for memory corruption beyond DoS in some toolchains/build configurations, but no evidence of reliable code execution has been provided in the available data. Analysts should treat the CVSS 6.1 score as the conservative, scoped impact.

Exploitation Scenarios

No public PoC is available; the attack chain below is inferred from the vulnerability class and the details in the NVD description. Only identifiers present in that description (CineonInput::open(), numberOfElements, strings[8], src/cineon.imageio/cineoninput.cpp) are used.

1. Reconnaissance / target identification. An attacker identifies a target environment that processes untrusted image assets with an application linked against a vulnerable OpenImageIO version (including VFX/rendering pipelines, asset-ingest services, thumbnailers, or cloud image-conversion services).

2. Craft the malicious file. The attacker creates or modifies a Cineon file and sets the numberOfElements field to a value greater than the maximum of eight. This value is the trigger for the vulnerability class.

3. Delivery and trigger. The file is delivered to the victim via standard user-execution vectors — e-mail attachment, shared asset library, download from a web resource, or submission to an automated image-processing service. When the victim application calls CineonInput::open() to parse the file, the unchecked numberOfElements value is used as the loop bound while the code fills the fixed strings[8] stack array, and the loop writes pointers beyond the end of that array.

4. Post-exploitation impact. The out-of-bounds writes corrupt adjacent stack memory. In the demonstrated impact this causes a crash (denial of service) and potentially corruption of nearby in-process state (Limited Integrity). Because the write primitive is present, memory-corruption exploitation is a theoretical concern in unhardened builds, but the data provided does not demonstrate such capability; SOC analysts should prioritize detecting crashes from malformed Cineon parsing.

Impact Assessment

• CVSS: 6.1 (Medium) — CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
• Confidentiality: None demonstrated. The corruption does not, per available data, disclose information.
• Integrity: Low. Adjacent state is written with pointer values, allowing limited in-memory corruption.
• Availability: High. The most reliably demonstrated outcome is process crash, which for image pipelines is a direct DoS.
• Attack requirements: Local vector plus user interaction — a victim must open/process the file. No privileges required.
• Scoped impact: Change only to the vulnerable component.

Blast radius. Any service, application, or pipeline component that parses Cineon images with affected OpenImageIO versions (below 3.0.20.0, 3.1.15.0, or 3.2.0.3-beta1). Automated ingest and rendering workers are the most exposed: a single malformed asset can crash every worker that touches it, cascading into render-farm outage. Because OpenImageIO is a library rather than a network service, exposure is proportional to how many untrusted image files the environment accepts, not to network reachability.

Detection Guidance

Sigma Rule

title: OpenImageIO Cineon Parsing Crash - CVE-2026-59181
id: 9c1f4a2e-5918-4b81-a6c1-0b7e2d6e1918
status: experimental
description: Detects process crashes associated with parsing of crafted Cineon image files exploiting a stack buffer overflow in OpenImageIO CineonInput::open()
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-59181
author: valtersit.com
date: 2026/01/01
logsource:
  category: application
  product: windows
  service: application
detection:
  selection_crash:
    Provider_Name: 'Application Error'
    Data|contains:
      - 'openimageio'
      - 'oiio'
      - 'cineon'
  selection_linux:
    type: 'SYSCALL'
    exe|endswith: 'oiio'
    key: 'process_exit'
  condition: selection_crash or selection_linux
fields:
  - CommandLine
  - Image
  - Faulting_Module_Name
falsepositives:
  - Legitimate malformed or truncated Cineon files in normal operation
level: medium
tags:
  - attack.t1204.002
  - cve.2026.59181

YARA Rule

rule CVE_2026_59181_OpenImageIO_Cineon_OOB
{
    meta:
        description = "Detects Cineon files with a numberOfElements value greater than the format maximum of eight, the trigger for CVE-2026-59181"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-59181"
        date = "2026-01-01"
        severity = "medium"

    strings:
        /* Cineon files begin with magic 0x802A5FD7 (big-endian) */
        $cineon_magic = { 80 2A 5F D7 }

    condition:
        $cineon_magic at 0
}

Note: This rule matches Cineon files heuristically by magic. It does not claim byte-precise validation of numberOfElements, because the header offset of that field is not provided in the available data; adding offset assertions would be speculative. Analysts should pair this with the crash detection above.

Suricata IDS Rule

Note: CVE-2026-59181 is a local file-parsing vulnerability with no network protocol component. There is no reliable network signature. The rule below is a placeholder that will not meaningfully detect this CVE and is provided only to meet format requirements.

alert tcp any any -> any any (msg:"CVE-2026-59181 - OpenImageIO Cineon OOB - NO NETWORK VECTOR (placeholder)"; flow:established,to_server; content:"|80 2A 5F D7|"; depth:4; classtype:attempted-dos; sid:202659181; rev:1; metadata:affected_product OpenImageIO, cve CVE_2026_59181;)

Analyst guidance: Detect this CVE through endpoint crash telemetry and file-integrity/AV scanning, not network IDS.

Elastic Detection

process where event.type == "end" and process.exit_code != 0 and
  process.name : ("oiio", "oiiotool", "maketx", "idiff") and
  process.args : "*.cin"

Companion EQL for library-linked hosts (crash telemetry):

process where event.action == "stopped" and
  process.name : ("blender", "nuke", "mari", "katana", "maya") and
  process.command_line : "*.cin"

Splunk SPL Query

index=main (sourcetype=WinEventLog:Application OR sourcetype=linux_syslog OR sourcetype=osquery)
  ("CineonInput::open" OR "cineoninput" OR "openimageio" OR "oiio" OR ".cin")
  (crash OR "segmentation fault" OR SIGSEGV OR SIGABRT OR "Faulting application" OR "stopped")
| stats count min(_time) as first_seen max(_time) as last_seen
        values(host) as hosts values(process_name) as processes
        by user, parent_process, file_name
| where count >= 1
| sort - count

Wazuh OSSEC Rule

<group name="openimageio,cve-2026-59181,image_parser,">
  <rule id="20259181" level="8">
    <decoded_as>json</decoded_as>
    <field name="program">oiiotool|oiio|maketx|idiff|blender|nuke</field>
    <regex type="pcre2">(?i)(cineon|\.cin\b|CineonInput)</regex>
    <regex type="pcre2">(?i)(segmentation fault|SIGSEGV|SIGABRT|stack smashing|corrupted|crash)</regex>
    <description>CVE-2026-59181: OpenImageIO Cineon parsing failed or crashed while processing .cin file (possible crafted numberOfElements overflow)</description>
    <mitre>
      <id>T1204.002</id>
    </mitre>
    <group>cve_2026_59181,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED — no patch evidence from any tracked source. No vendor advisory URL, commit hash, or fix artifact is available in the provided data beyond the version numbers stated in the NVD description. Treat all patching actions as verification-required.

1. Immediate mitigations.

   • Block or quarantine .cin (Cineon) file ingest at the mail gateway, upload endpoints, and asset-management front doors until OpenImageIO can be upgraded. If Cineon support is not a business requirement, remove or disable the Cineon imageio plugin from OpenImageIO builds entirely.
   • Isolate image-processing/rendering workers from internal resources and apply resource limits (CPU, memory, restart supervision) so that a crash of one worker does not cascade across the render farm.
   • Enforce deny-by-default allow-listing of image file extensions on ingest services; reject Cineon files from untrusted sources.

2. Patch / upgrade steps.

   • Upgrade OpenImageIO to 3.0.20.0, 3.1.15.0, or 3.2.0.3-beta1 (or later) as stated in the NVD description. Verify the fix by confirming CineonInput::open() in src/cineon.imageio/cineoninput.cpp bounds the numberOfElements loop before writing to strings[8].
   • Because no official advisory URL was located in the provided data, validate upgrade artifacts against the project's official release channel and record hashes.
   • Inventory indirect consumers: any application embedding OpenImageIO (rendering engines, asset managers, DCC tools) must be rebuilt or updated. Check dependency manifests for embedded OpenImageIO copies.

3. Long-term hardening.

   • Compile image parsers with stack-protector-strong, -D_FORTIFY_SOURCE=2, and ASAN instrumentation in CI to catch out-of-bounds writes in parser code during fuzzing.
   • Add fuzzing harnesses for CineonInput::open() and the broader Cineon header parser to regression-test all count/size fields against their defined maxima.
   • Adopt a secure-parsing policy for all imageio plugins: never trust header-declared counts as loop bounds against fixed-size stack buffers; validate against the format maximum before use.
   • Monitor OpenImageIO releases and CVE feeds for this CVE ID until a vendor advisory with a patch reference is published; reassess patch confidence at that time.

References

1. NVD — CVE-2026-59181: https://nvd.nist.gov/vuln/detail/CVE-2026-59181
2. OpenImageIO project repository and release notes (consult the official OpenImageIO source for version 3.0.20.0, 3.1.15.0, and 3.2.0.3-beta1 release information): https://github.com/AcademySoftwareFoundation/OpenImageIO
3. CWE-121 — Stack-based Buffer Overflow: https://cwe.mitre.org/data/definitions/121.html
4. MITRE ATT&CK T1204.002 — User Execution: Malicious File: https://attack.mitre.org/techniques/T1204/002/
5. CISA Known Exploited Vulnerabilities catalog — CVE-2026-59181 not listed as of report date: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Threat actor / exploit-in-the-wild status: No public PoC, no exploit code, no Nuclei template, and no CISA KEV listing were identified in the provided data. EPSS has not been scored by FIRST.org. The exploitation scenario in this report is inferred from the vulnerability class; no campaign or actor attribution is available or claimed.