CVE-2025-29485: Libming DoS Vulnerability via Segfault

CVE-2025-29485 Overview

CVE-2025-29485 is a denial of service vulnerability in libming v0.4.8, an open source library for generating Shockwave Flash (SWF) files. The flaw resides in the decompileRETURN function, which triggers a segmentation fault when parsing a specially crafted SWF file. An attacker can weaponize a malicious SWF to crash any application or tool that links against the vulnerable library. The issue is tracked under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). Exploitation requires the victim to open or process the crafted file, but no authentication is needed.

Critical Impact
A crafted SWF file processed by libming v0.4.8 causes a segmentation fault in decompileRETURN, resulting in application termination and denial of service.

Affected Products

libming libming 0.4.8
Applications and utilities (including swftophp and other libming-based tools) that link against libming 0.4.8
Downstream distributions packaging libming 0.4.8

Discovery Timeline

2025-03-27 - CVE-2025-29485 published to the National Vulnerability Database
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-29485

Vulnerability Analysis

The vulnerability affects the SWF decompilation logic in libming v0.4.8. When the library encounters a malformed return instruction inside a crafted SWF file, execution reaches decompileRETURN with unexpected stack or buffer state. The function fails to validate its inputs before performing memory operations, and the process terminates with a segmentation fault. This behavior is consistent with [CWE-119], where the code operates outside the intended memory bounds. Because SWF parsing is often performed as part of automated pipelines, converters, or file previewers, the crash reliably disrupts service. The vulnerability does not appear to enable code execution based on available public information, but repeated crashes can be used to disable file processing services.

Root Cause

The root cause is missing bounds and state validation inside the decompileRETURN function during SWF bytecode decompilation. The function assumes the internal decompilation stack contains valid data when processing a RETURN opcode. A crafted SWF supplies conditions that violate this assumption, leading to an invalid memory access and a segmentation fault. The issue is tracked in the upstream libming GitHub issue #330.

Attack Vector

Exploitation is remote but requires user interaction. An attacker delivers a malicious SWF file through email, a web download, or a file upload endpoint. When the victim opens the file with a tool built on libming 0.4.8, such as swftophp, the process crashes. Server-side automation that decompiles SWF files can be knocked offline by feeding the crafted input into the processing queue. A public proof of concept is referenced in the GitHub PoC Repository.

No verified exploit code is republished here. The vulnerability mechanism is described in the referenced advisory, and reproduction requires the crafted SWF sample linked from the PoC repository.

Detection Methods for CVE-2025-29485

Indicators of Compromise

Repeated segmentation fault entries in system logs referencing swftophp, libming, or any process linking libming.so.0.4.8.
Core dumps whose stack traces include the decompileRETURN symbol from libming.
Untrusted SWF files arriving via email gateways, upload endpoints, or file conversion pipelines.

Detection Strategies

Hunt for SIGSEGV termination events in application and container logs that correlate with SWF file processing.
Inspect ingress SWF files for anomalous or malformed bytecode using file carving and format validators before they reach libming.
Correlate crash events with the file hash of the input to identify a recurring malicious sample.

Monitoring Recommendations

Enable core dump collection on hosts running libming-based converters so crashes can be triaged rather than silently restarted.
Alert on abnormal restart rates of services that consume SWF input, which often indicates a crash loop triggered by malicious files.
Track outbound file transfer of SWF samples paired with process crashes to identify targeted delivery attempts.

How to Mitigate CVE-2025-29485

Immediate Actions Required

Inventory all hosts, container images, and build artifacts that ship libming 0.4.8 or its shared object libming.so.
Remove or disable SWF processing utilities such as swftophp on servers that do not require them.
Reject SWF uploads at the network edge until libming can be replaced or hardened.

Patch Information

At the time of publication, no fixed release of libming addressing CVE-2025-29485 has been published by the maintainers. Track the upstream libming GitHub issue #330 for status updates. Downstream Linux distributions may issue backported fixes; monitor their security trackers and apply updates when available.

Workarounds

Run libming-based converters inside a sandbox or ephemeral container so a segmentation fault does not affect the host or shared services.
Enforce strict file type validation and size limits on SWF uploads, and quarantine files that fail structural checks.
Migrate away from SWF processing where feasible, since Adobe Flash and its file format are end-of-life.
Apply automatic service supervision with rate limiting so a crash loop triggered by a malicious file does not consume host resources.

bash

# Example: contain swftophp execution with resource limits and a temporary filesystem
systemd-run --scope --uid=nobody --gid=nogroup \
  -p MemoryMax=256M -p CPUQuota=25% -p PrivateTmp=yes -p NoNewPrivileges=yes \
  swftophp /var/uploads/untrusted.swf > /dev/null