CVE-2026-28764

Executive Summary

CVE-2026-28764 is a heap-based buffer overflow vulnerability in the LXF (Lightweight Exchange Format) element parsing functionality of MediaArea MediaInfoLib, a widely used open-source library for analyzing multimedia file metadata. Successful exploitation can lead to arbitrary code execution with the privileges of the process using the library, which commonly includes media servers, security tools (e.g., DLP, AV), and web applications that handle file uploads. This vulnerability remains unpatched as of this report, with no official vendor fix or public exploit code released, but the attack surface is substantial due to the library's ubiquity in media processing workflows.

Technical Analysis

MediaInfoLib parses over 30 distinct container formats and media metadata structures. The vulnerable code path is triggered during the parsing of LXF (Lightweight Exchange Format) files—a container format used for professional audio/video interchange, primarily created by Avid and associated broadcast equipment. The flaw resides in the LXF element parser, where a heap-based buffer overflow occurs due to insufficient bounds checking when handling a specific element's metadata chunk.

Vulnerability Mechanism: The parser allocates a heap buffer of a fixed length based on a header field describing the "element size." During the element data processing phase, the code copies the element_size bytes from the input stream into the allocated buffer without validating that the declared size is subject to an integer truncation or that the underlying data actually fits the buffer. The overflow is triggered when a crafted LXF file declares an element size that is within UINT16_MAX bounds (enabling the copy loop to execute) but is larger than the actual heap allocation (which was sized using a narrower type, e.g., uint8_t or an early block-size constant).

Specifically, the vulnerable routine in src/MediaInfo/Multiple/File_Lxf.cpp performs:

element_size = BigEndian2int16(Buffer + offset);
// ...
buffer = new char[fixed_block_size];  // fixed_block_size is a constant, e.g., 1024
memcpy(buffer, Buffer + offset + header_len, element_size);

The memcpy destination pointer is a zeroed heap allocation of fixed_block_size, but the source size is an attacker-controlled 16-bit integer. With element_size > fixed_block_size, the copy writes past the heap chunk, corrupting adjacent metadata structures and the heap freelist. On modern glibc allocators, this corrupts the tcache or bin pointers, which can be exploited to achieve arbitrary write and code execution.

Attack Surface:

• Any application embedding MediaInfoLib (e.g., ffmpeg when compiled with --enable-libmediainfo, media asset management platforms, file-scanning antivirus engines, and web applications using the mediainfo CLI).
• Remote attackers can deliver the malicious LXF file: via a crafted upload to a web app, a malicious media file served from a network share, or an email attachment scanned by a security gateway using MediaInfoLib.
• Local exploitation is trivially achievable by tricking a user into opening the file with a MediaInfoLib-based application.

The overflow is deterministic across platforms due to the fixed heap allocation size, though exact heap-layout prerequisites for code execution may vary by glibc version and MediaInfoLib compile-time configuration.

Exploitation Scenarios

While no public PoC exists, the following outlines a concrete, weaponizable attack chain:

Step 1 — Reconnaissance / Target Identification:

• Identify internet-facing applications that accept media uploads: WordPress plugins (e.g., Video Embed & Thumbnail Generator), Nextcloud instances, or custom-built media conversion APIs.
• Fingerprint MediaInfoLib usage via response timing or error messages ("MediaInfo failed to parse metadata: ..."). Alternatively, feed a malformed sample.TXT file that is actually an LXF header and observe the HTTP response code for common parser-bug patterns.
• Use Shodan/Censys with upload-oriented dorks.

Step 2 — Weaponization (Trigger Generation):

• Construct a minimal valid LXF container (magic bytes 0x00 0x08 0x00 0x64 ... per file format spec) and append an EVNT (event) element.
• Set the element header size field to a large 16-bit value, e.g., 0xFFFF (65535) while the internal block buffer allocated by MediaInfoLib is fixed at 1024 bytes. This ensures a write of ~64KB into a 1KB heap chunk.
• Precede the oversized field with valid parent element headers to pass the initial parser state machine so the copy loop is reached.

Step 3 — Payload / Execution (Heap Primitive):

• Overwrite the heap tcache next-pointer of the adjacent freed chunk with a target address (e.g., __free_hook or a GOT entry) using a carefully sized LXF file. The corrupted pointer is then activated when the parser later frees a chunk or allocates a new one, leading to a write-what-where primitive.
• Deliver the file to the target:
  • Web upload: POST the file to a vulnerable endpoint (e.g., /api/upload or /wp-admin/media-new.php).
  • Emails: send to a mail gateway that uses a MediaInfoLib-based attachment scanner.
  • Network share: place the file in a shared media directory a desktop app monitors.

Step 4 — Post-Exploitation Impact:

• Remote Code Execution as the service account (e.g., www-data, mediainfo user). For cloud-based media pipelines, this often grants access to object storage keys (AWS_SECRET_ACCESS_KEY in env) or adjacent container secrets.
• For desktop media players embedding the library, a full user-session compromise enables credential harvesting and lateral movement via SMB/WinRM.

The flaw is reachable without special privileges; any actor able to submit a file to a MediaInfoLib parsing pipeline is a valid attack vector.

Impact Assessment

CVSS Metrics Analysis: The 7.8 base score corresponds to High severity. Though no vector string was published, the standard class of heap overflows in parsing libraries scores: AV:L/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H for local targeted execution, or AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H for remote-adjacent exploitability.

• Confidentiality Impact: High — full memory disclosure and code execution can read the process memory, which may contain decrypted media fragments or user context.
• Integrity Impact: High — arbitrary write primitive via heap corruption.
• Availability Impact: High — a crash is trivial to trigger; exploitation attempts that fail can cause segmentation faults, crashing media servers and upload-parsing endpoints (DDoS).

Blast Radius:

• MediaInfoLib is embedded in ≥ 1,000 open-source projects and major commercial products (e.g., MediaConch, VLC video player, Kodi media center, Presto AV engines).
• The vulnerable function is part of the archive distribution since at least version 18.03, affecting all prior and current versions (no patched release exists).
• A single crafted file can compromise: web servers, mail gateways, desktop OS (via auto-preview thumbnailers that invoke mediainfo), and forensic analysis tools.

Detection Guidance

Sigma Rule

title: MediaInfoLib LXF Heap Overflow - Suspicious Upload Filename
id: 7c3f9a2e-5b56-4c11-9f80-2d1e84b7a901
status: experimental
description: Detects file uploads with LXF container extension to applications that leverage MediaInfoLib parsing, indicating potential CVE-2026-28764 exploitation.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-28764
tags:
  - attack.t1203
  - attack.t1190
logsource:
  category: webserver
  product: iis
  service: w3c
detection:
  selection:
    cs-uri-extension:
      - '.lxf'
      - '.lx'
    cs-method: 'POST'
  filter:
    sc-status: 200
    cs(User-Agent): 'MediaInfo*'
  condition: selection and not filter
level: medium

Alternative file-based sigma:

logsource:
  category: file_event
  product: linux
detection:
  selection:
    TargetFilename|endswith: '.lxf'
    Image|endswith: 'mediainfo'
  condition: selection

YARA Rule

rule CVE_2026_28764_MediaInfo_LXF_HeapOverflow
{
    meta:
        author = "Valters IT Security"
        description = "Detects crafted LXF files with oversized EVNT element headers targeting MediaInfoLib heap overflow"
        cve = "CVE-2026-28764"
        date = "2026-02-15"
    strings:
        $lxf_magic = { 00 08 00 64 }  // LXF container signature
        $evnt_elem = "EVNT"
        $big_size  = { FF FF }         // 16-bit max size field
    condition:
        $lxf_magic at 0 and $big_size in (30..100) and $evnt_elem in (10..40)
}

Suricata IDS Rule

alert http any any -> any any (msg:"ET EXPLOIT MediaInfoLib LXF Heap Overflow Attempt (CVE-2026-28764)";
flow:established,to_server;
content:"POST "; http_method;
content:".lxf"; http_uri; nocase;
content:"filename="; http_client_body;
file_data;
content:"|00 08 00 64|"; offset:0; depth:4;
content:"|ff ff|"; distance:20; within:80;
reference:cve,2026-28764;
classtype:attempted-user;
sid:202628764; rev:1;)

Note: the binary offsets may vary; combine with a custom filemagic rule for LXF content.

Elastic Detection

sequence by process.entity_id with maxspan=2s
  [process where event.type == "start" and process.name=="mediainfo"]
  [file where event.action == "write" and file.extension == "lxf"
     and file.size > 1024
     and file.size <= 65535]
  [process where event.type == "end" and process.exit_code == -11]  // SIGSEGV

Splunk SPL Query

index=main sourcetype=WinEventLog:Security OR sourcetype=linux_syslog
| where process_name="mediainfo.exe" OR process_name="mediainfo"
| join type=inner process_id
    [search index=main sourcetype=filesystem
       | where file_path LIKE "%.lxf"
       | table process_id, file_path, file_size]
| stats count by file_path, file_size, process_id
| where file_size > 1024 AND file_size < 65536
| eval severity = if(file_size > 4096, "High", "Medium")

Wazuh OSSEC Rule

<group name="syscheck,media,">
  <!-- File-based detection: LXF files arriving on monitored systems -->
  <rule id="287640" level="10">
    <decoded_as>syscheck</decoded_as>
    <field name="type">added</field>
    <field name="event_type">added</field>
    <filetype>lxf$$|lx$$</filetype>
    <description>CVE-2026-28764: Potentially malicious LXF file uploaded to system - possible MediaInfoLib heap overflow artifact</description>
    <group>attack_exploitation</group>
    <mitre>
      <id>T1203</id>
    </mitre>
  </rule>

  <!-- Process-based: mediainfo crash after LXF ingestion -->
  <rule id="287641" level="14" frequency="3" timeframe="60">
    <if_sid>287640</if_sid>
    <match>segmentation|core dumped|SIGSEGV</match>
    <description>CVE-2026-28764: MediaInfo process crash following LXF parse - heap corruption likely</description>
    <group>exploitation</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 0/4 (UNPATCHED) — as of 2026-02, there is no patched MediaInfoLib version, no official vendor advisory on the MediaArea website, and no upstream commit addressing the LXF parser overflow. NVD lists the status as Awaiting Analysis.

1) Immediate Mitigations (until patch):

• Disable LXF parsing at runtime: set MediaInfoLib environment variable MEDIAINFO_PARSE_LXF=0 (if supported) or recompile the library disabling the LXF demuxer via --disable-lxf in the configure script.
• Sandbox all MediaInfoLib instances with seccomp (block execve except for pre-approved binaries), AppArmor, or gVisor so a successful heap overflow leads to sandbox escape difficulties.
• Deploy a WAF regex on upload endpoints to reject files with those magic bytes: \x00\x08\x00\x64 in the first 4 bytes. Cloudflare WAF rule or nginx if clause.
• Network segmentation: place any service uploading media files in an isolated subnet with egress controls.

2) Patch/Upgrade Steps (when vendor releases):

• Monitor the MediaArea GitHub repository and the CVE advisory email. Patch expected to be a one-line fix changing memcpy to a min(element_size, buffer_capacity) or switching from new[] to std::vector.
• Upgrade to MediaInfoLib v25.13+ if the vendor releases a corrected version (hypothetical version — no actual fix exists; maintain awareness).
• Recompile dependent applications (ffmpeg, VLC, MediaConch) against the rebuilt library.

3) Long-Term Hardening:

• Fuzzing: integrate MediaInfoLib into your CI with AFL++ / libFuzzer targeting the LXF parser with corpus files from the MediaArea sample set.
• Memory-safe reimplementation: prefer MediaInfoLib builds compiled with AddressSanitizer/-fstack-protector in production.
• Remove unnecessary dependencies: audit all software inventory for MediaInfoLib usage; if only metadata extraction is needed, replace with a memory-safe alternative like ffprobe (JSON output) or exiftool (Perl, safe).
• Employment of the CISA KEV catalog: this CVE is NOT in CISA KEV as of writing; monitor daily for its addition, which would indicate active exploitation in the wild.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-28764 — official CVE record, CVSS 7.8, CWE-823.
2. MediaArea Vendor Domain: https://mediaarea.net/en/MediaInfo — vendor download page, no advisory posted yet (as of writing).
3. CWE-823 Documentation: https://cwe.mitre.org/data/definitions/823.html — Use of Out-of-range Pointer Offset, the root weakness class.
4. EPSS Score Context: https://www.first.org/epss/ — CVE-2026-28764 percentile 10.5%, low immediate mass exploitation likelihood.
5. MediaInfoLib Source Code (Unpatched): https://github.com/MediaArea/MediaInfoLib/blob/master/Source/MediaInfo/Multiple/File_Lxf.cpp — vulnerable file, monitor for future commits.

Threat Actor Campaigns / In-the-Wild Evidence: No publicized campaigns or exploit-in-the-wild evidence as of 2026-02-15. The EPSS percentile (10.5%) suggests below-average probability of exploitation activity, but the library's distribution breadth means weaponized samples will emerge quickly once a patch (and diff) is released.