CVE-2025-14369

Executive Summary

CVE-2025-14369 identifies an integer overflow vulnerability in dr_flac, the audio decoding component of the dr_libs toolset (developed by certcc). The flaw arises from a trust relationship established with the totalPCMFrameCount field embedded in FLAC metadata before buffer size calculations are performed. An attacker capable of crafting a malicious FLAC file can trigger this vulnerability to cause a denial of service (DoS) against any application that embeds and utilizes the dr_flac decoder. The affected population is broad: any software project—from security tools to multimedia applications—that statically links or vendors the dr_libs library is potentially vulnerable. The CVE has been assigned, and two independent sources (CNA and OSV) confirm a patch is likely available, but no official fix version or advisory has been publicly released.

Technical Analysis

The vulnerability resides in the dr_flac component of the dr_libs project—a widely vendored collection of single-file public-domain libraries for audio decoding (FLAC), image processing, and other media formats. Due to the library's design philosophy of being embedded directly into downstream projects via a single source file, its reach extends far beyond its host repository.

Vulnerability Mechanism — Trusted Metadata Leading to Integer Overflow:

The core flaw is a classic integer overflow scenario stemming from excessive trust in attacker-controlled input. FLAC (Free Lossless Audio Codec) files carry a STREAMINFO metadata block that, among other fields, declares the totalPCMFrameCount—a 36-bit unsigned integer describing the number of PCM frames in the audio stream.

The vulnerable code path is as follows:

1. The dr_flac decoder parses the FLAC file and reads the totalPCMFrameCount field from the STREAMINFO metadata block.
2. Without adequate validation of the field's magnitude, the decoder uses this value to calculate the required memory buffer size for PCM samples.
3. The buffer size calculation involves multiplying totalPCMFrameCount by the number of channels and the bit depth per sample (bytes per sample).
4. When totalPCMFrameCount is set to an extremely large value (approaching the maximum representable integer), the multiplication overflows the integer boundary (typically 32-bit int or size_t on 32-bit systems), producing a small, undersized allocation.
5. Subsequent write operations—which are calculated using the original large totalPCMFrameCount value—exceed the allocated buffer bounds, resulting in a heap-based buffer overflow. This memory corruption characteristically leads to segmentation faults, heap corruption, or an application crash.

Distinguishing feature: The NVD description explicitly notes the flaw is due to "trusting the totalPCMFrameCount field from FLAC metadata before calculating buffer size." This implies the missing step is a sanity check comparing the declared frame count against a maximum plausible value (e.g., derived from file size, stream duration, or a hard-coded cap). The decoder should reject the stream or reallocate dynamically, but instead it computes a static allocation predicated on an unvalidated user-controlled number.

Attack Surface:

• File parsing: Any code path that feeds a FLAC file (local file, fetched over a network, or extracted from a container archive) into dr_flac exposes this vulnerability.
• Vendor supply chain: Due to the copy-paste style distribution of dr_libs, many applications embed the code without tracking updates via system package managers. A single vulnerable copy may persist for years, unnoticed by automated vulnerability scanners that only track OS-level packages.
• No authentication required: If an application processes untrusted or semi-trusted FLAC files (e.g., a media player that loads files from mounted directories, a chat client that auto-decodes audio previews, or a server-side audio analysis tool), the attack is delivered simply by enticing a target to open a file.

It is important to note that the NVD description does not specify the exact vulnerable function name or whether the overflow is in a single-allocation path or a streaming reallocation path. Given the phrasing "before calculating buffer size," it is likely in a function that transitions from header parsing to full-stream decoding (e.g., a function named similarly to drflac_open_* and the subsequent internal decode functions). Insufficient technical detail is available to specify exact line-level code.

Exploitation Scenarios

No public PoC or exploit code is available for CVE-2025-14369. The following attack chain is inferred from the vulnerability class and the NVD description. It is an integer-overflow-leading-to-heap-buffer-overflow scenario, not a logic bypass.

Step 1 — Reconnaissance/Target Identification: The attacker's challenge is identifying software that statically links dr_flac. This is not publicly indexable via standard fingerprinting (e.g., no HTTP headers reveal the use of dr_libs). An attacker would instead:

• Target popular multimedia applications, audio converters, or game engines known to use single-file audio decoders (publicly documented via source code audits).
• Target platforms where users routinely download and open uncategorized audio files (forums, file-sharing sites, messaging apps).
• Alternatively, poison a source code repository or a package mirror by submitting a malicious FLAC file as a test fixture, triggering the bug in CI/CD pipelines that invoke the audio decoder on sample files.

Step 2 — Triggering the Flaw: The attacker crafts a minimal valid FLAC file. The file must contain:

• A correct FLAC header and a STREAMINFO metadata block.
• Inside STREAMINFO (offset based on standard FLAC format), a totalPCMFrameCount field (36 bits) filled with a value close to 2^36 - 1 (~68.7 billion frames).
• Matching or minimal channel count and bit depth fields so the file passes initial structural validation.
• Followed by a minimal amount (or even zero) actual audio frame data—the crash occurs during allocation/decoding setup after header parsing, likely before any frame is decoded.

When the vulnerable decoder parses this file, the arithmetic overflow in the buffer-size calculation produces an undersized heap allocation. The decoder then proceeds to decode the stream into this undersized buffer, causing out-of-bounds writes.

Step 3 — Payload Execution at the Class Level: At the vulnerability-class level (integer overflow → heap buffer overflow), the attacker does not control arbitrary memory contents directly—they control the length values that lead to the overflow. The overwritten memory beyond the allocated chunk will contain zeros or partial PCM frame data derived from the file contents. A deterministic crash is achievable by simply causing the decoder to write past the boundary, corrupting heap metadata and triggering an abort on free() or malloc() revalidation.

For more impactful exploitation (e.g., remote code execution), the attacker would need to:

• Carefully shape heap layout to put a sensitive pointer (function pointer, vtable) adjacent to the overflow buffer.
• Control the values written via the crafted file's header/data bytes.
• Survive the inevitable heap corruption long enough to redirect execution.

Given the complexity of FLAC frame layout and the lack of public research on this specific overflow's write primitives, reliable RCE is unlikely; the pragmatic impact is a guaranteed process crash (DoS).

Step 4 — Post-Exploitation Impact: With the process terminated, the service or application fails. For a server-side component that processes audio uploads (e.g., a transcription service), a single malicious file can crash the worker. Repeated crashes could lead to resource exhaustion and availability loss. If the application is long-running with no crash-restart mechanism, the DoS is permanent until manual intervention.

Impact Assessment

Business Impact — Availability (Primary):

The impact is singular and clear: Denial of Service. An attacker can crash a process with a small, easily-crafted file. The affected service must restart to resume operation. In a microservice or pipeline architecture, a crafted file can be replayed indefinitely, causing sustained availability loss.

The lack of a CWE designation and CVSS score in the NVD data makes quantitative scoring difficult. Based on the vulnerability class (integer overflow → heap overflow, local file-based trigger), one can estimate a CVSS v3.1 score in the range of 5.5–6.5 (Medium), with a vector resembling AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H or AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H if the file is fetched over a network by the vulnerable application.

Affected Systems & Blast Radius:

• Directly affected: Any application embedding dr_flac (or the full dr_libs amalgamation) with a version prior to the patched commit.
• Blast radius expansion: Because dr_libs is a single-header library that downstream developers copy verbatim into their source trees, there is no authoritative registry to query for affected applications. The "unknown unknowns" are significant. Third-party applications that vendor dr_libs and do not track upstream updates will remain vulnerable indefinitely.
• EPSS Score: 0.00153 (4.7th percentile)—low exploitation probability in the wild currently, consistent with a newly disclosed vulnerability without public PoC.
• CISA KEV: Not listed—no known exploitation in the wild.

Detection Guidance

Detection of this vulnerability is challenging because it is a file-parsing bug triggered by specific, malformed binary data rather than a network-detectable exploit pattern. Detection strategies hinge on behavioral monitoring (crashes, abnormal memory allocations) and static binary audit rather than signature-based network detection. The following rules are therefore realistic, if imperfect, indicators.

Sigma Rule

title: Heap Corruption Crash in dr_flac Audio Decoder (CVE-2025-14369)
id: 7b6c2b8e-4c3a-4e4b-9c5f-2a3b4c5d6e7f
status: experimental
description: Detects process crashes or abnormal aborts consistent with heap overflow in dr_flac audio decoding.
author: Valtersit Threat Intel
logsource:
    product: windows
    category: application
detection:
    selection_crash:
        EventID: 1000  # Application Error
        Application:
            - '*'
        ModuleName:
            - '*.exe'
            - '*.dll'
    selection_exception:
        EventID: 1001  # Windows Error Reporting
        FaultingModule:
            - '*dr_flac*'
            - '*dr_libs*'
    selection_memory:
        EventID: 1002  # Application Hang
    condition: selection_crash or selection_exception or selection_memory
level: medium
falsepositives:
    - Legitimate crashes from other causes are common; this rule is noisy unless tuned per application.
    - Requires access to Windows Event Logs, which is uncommon in containerized environments.
fields:
    - EventID
    - Application
    - FaultingModule
    - Message

YARA Rule

/*
   Detects FLAC files with a STREAMINFO block containing
   a suspiciously large totalPCMFrameCount (36-bit field)
   that may trigger integer overflow in dr_flac (CVE-2025-14369).
*/
rule CVE_2025_14369_FLAC_totalPCMFrameCount_Overflow
{
    meta:
        author = "Valtersit Threat Intel"
        description = "Detects FLAC files with excessive totalPCMFrameCount indicating crafted exploit file"
        cve = "2025-14369"
        date = "2025-01-01"
        severity = "medium"
    strings:
        // FLAC file signature and STREAMINFO framing hint
        $flac_magic = "fLaC"
        // STREAMINFO block type (last-block flag (0x80) + block type 0) - arbitrary padding for detection
        $streaminfo_block = { 80 00 00 00 22 }
    condition:
        uint32be(0) == 0x664C6143 and // "fLaC" at file start
        $streaminfo_block at 4 and
        // parse totalPCMFrameCount typically at offset 10 (within STREAMINFO 34 byte block)
        // 36-bit value spanning bytes 10-14; check if high 4 bits are set (value > 2^31)
        (uint32be(10) & 0xFFFF0000) > 0 and
        (uint32be(10) & 0x80000000) == 0x80000000
}

Suricata IDS Rule

Suricata is a network-based IDS. Application-level parsing bugs triggered by file content are only detectable if the network traffic transports the raw file over unencrypted channels (e.g., HTTP download of an audio file). The rule below is of limited practical value for encrypted traffic or local file access.

alert http any any -> $HOME_NET any (
    msg:"Potential CVE-2025-14369 FLAC File Delivery - Large totalPCMFrameCount";
    flow:established,to_client;
    file.magic;
    fileext:"flac";
    content:"fLaC";
    pcre:"/\x80\x00\x00\x00\x22.{6}(\x10\x00\x00\x00).{16}/s";
    sid:202514369;
    rev:1;
    metadata:attack_target Client_Endpoint, created_at 2025_01_01, deployment Perimeter, signature_severity Major, cve 2025 14369;
)

Note: This is a heuristic rule—it inspects the raw FLAC STREAMINFO metadata fetched over HTTP. Legitimate high-resolution FLAC files can have large frame counts; the rule may produce false positives and is not a reliable primary detection method.

Elastic Detection

// EQL Query: Detect process crashes stemming from heap corruption likely caused by FLAC parsing
sequence with maxspan=5m
  [ process where event.type == "start" and process.name == "audio_parser.exe" ] // Example app name
  [ process where event.type == "end" and process.exit_code == 0xC0000409 ] // STATUS_STACK_BUFFER_OVERRUN / Security check
  // OR common heap corruption exit codes: 0xC0000374 (STATUS_HEAP_CORRUPTION)

Splunk SPL Query

index=windows sourcetype=WinEventLog:Application EventCode=1000 OR EventCode=1001
| where FaultingModule=* OR Application=*
| search "*dr_flac*" OR "*heap*" OR "*STATUS_HEAP_CORRUPTION*" OR "*0xc0000374*"
| stats count by host, Application, FaultingModule, TimeGenerated
| table host, Application, FaultingModule, count

Wazuh OSSEC Rule

<group name="cve_2025_14369,">
  <!-- Rule for Linux environments where dr_flac-based app crashes with SIGSEGV/SIGABRT -->
  <rule id="2025143" level="10">
    <decoded_as>syslog</decoded_as>
    <field name="program_name">kernel</field>
    <regex>segfault at</regex>
    <description>CVE-2025-14369 potential heap overflow crash in dr_flac audio decoder - process segfaulted</description>
    <group>local_policy,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 3/4 (LIKELY) — Two independent sources (CNA and OSV) confirm that a fix exists. However, the vendor has not released a public advisory or a fixed version number through the NVD channel. OSV shows the package remaining in an "unfixed" state with version "/" (0→unfixed), indicating that while the fix commit may exist in the upstream repository, it has not been released as a tagged version, and downstream users must update from the source tree.

1. Immediate Mitigations:

   • If your application statically links dr_flac or dr_libs, immediately discontinue processing untrusted FLAC files. If FLAC support is not a core business function, disable the feature or introduce a file-type allowlist.
   • If the application provides audio parsing to end users, isolate the parsing in a separate, low-privilege process (sandbox/container) so a crash does not affect the main application.
   • Monitor crash logs and bug reports for spikes in heap corruption errors in the audio parsing module.

2. Patch/Upgrade Steps:

   • Upstream vendor: The fix has been applied upstream (per CNA/OSV sources). Download the latest version of dr_libs from the official repository (https://github.com/mackron/dr_libs) and replace the dr_flac.h (or amalgamated dr_libs.h) header in your codebase.
   • Audit for vendored copies: Because the library is distributed as a single copy-paste C header, search your entire source tree and CI pipelines for any copy of dr_flac.h or references to dr_flac_open/drflac—these may be copied into multiple projects.
   • Version pinning: There is no stable version number yet. Verify the fix commit by checking the repository's commit history for changes addressing totalPCMFrameCount validation and the buffer-size calculation logic.

3. Long-Term Hardening:

   • Dependency tracking: For single-header libraries, maintain an inventory (even a simple text file) of the upstream version or commit SHA of each embedded library. Subscribe to watch notifications for upstream repos that you vendor.
   • Fuzzing: Regularly fuzz the audio decoding library with a fuzzer (AFL++, libFuzzer) using structured FLAC files. This vulnerability class is readily discoverable via fuzzing with assertions and AddressSanitizer enabled.
   • Input validation: At the application boundary, parse and validate the STREAMINFO metadata block before passing it to the decoder. Reject files with a declared frame count inconsistent with the physical file size (e.g., file_size / 1 byte-per-frame heuristic).
   • Code audit: Once patched, review the upstream fix diff to understand the allowed validation logic; ensure the fix does not merely cap totalPCMFrameCount at an arbitrary value but properly handles large allocations with overflow checks.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-14369 — NVD record containing the description and patch references (CNA, OSV).
2. OSV Record: https://osv.dev/vulnerability/CVE-2025-14369 — Open Source Vulnerability database confirming package state and patch indication.
3. dr_libs Official Repository: https://github.com/mackron/dr_libs — Upstream source repository for dr_flac.h, the vulnerable component; the fix should be located in commit history.
4. CWE-190 Integer Overflow Reference: https://cwe.mitre.org/data/definitions/190.html — Similar vulnerability classes and remediation patterns.
5. MITRE ATT&CK Technique T1499 (Endpoint Denial of Service): https://attack.mitre.org/techniques/T1499/ — Relevant technique mapping for the adversarial goal of resource exhaustion via crash.

Threat Actor Activity: No active campaigns, exploit-in-the-wild evidence, or known threat actor utilization of CVE-2025-14369 exists as of the intelligence reporting date. The EPSS score of 0.00153 and absence from CISA KEV confirm no observed exploitation activity.