CVE-2025-63095: Hello-video-codec DoS Vulnerability

CVE-2025-63095 Overview

CVE-2025-63095 is an improper input validation vulnerability [CWE-20] in the BitstreamWriter::write_bits() function of Tempus Ex hello-video-codec version 0.1.0. Attackers can send crafted input to trigger a Denial of Service (DoS) condition against applications that link the affected codec library. The flaw exists in the Rust source file src/bitstream.rs within the project repository. Exploitation requires user interaction but does not require authentication or privileges. No public proof-of-concept exploit or in-the-wild exploitation has been reported.

Critical Impact
Remote attackers can crash applications using hello-video-codec 0.1.0 by supplying malformed input to the bitstream writer, disrupting availability of dependent video processing workflows.

Affected Products

Tempus Ex hello-video-codec version 0.1.0
Applications embedding the tempus-ex:hello-video-codec Rust crate
Downstream video processing pipelines linking the vulnerable bitstream.rs module

Discovery Timeline

2025-12-01 - CVE-2025-63095 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-63095

Vulnerability Analysis

The vulnerability resides in the BitstreamWriter::write_bits() function implemented in src/bitstream.rs of the hello-video-codec project. The function writes a variable number of bits into an internal bitstream buffer but fails to properly validate the input parameters that control the write operation. When an attacker supplies crafted input, the function enters an error state that terminates the process, producing a Denial of Service. Because the codec is invoked when processing untrusted video data, the flaw is reachable over network-delivered content once a user opens or streams a malicious file. The impact is limited to availability; confidentiality and integrity are not affected.

Root Cause

The root cause is missing bounds and range validation on parameters passed to write_bits(). The function does not verify that the requested bit count and value combination remain within safe operating bounds before performing shift and buffer operations. Rust's runtime checks then abort execution rather than silently corrupting memory. This behavior converts what would otherwise be undefined behavior into a deterministic panic, categorized under [CWE-20] Improper Input Validation.

Attack Vector

Exploitation is network-reachable and requires user interaction, such as opening or playing a crafted media asset processed by an application that embeds hello-video-codec 0.1.0. The attacker crafts input that causes write_bits() to receive out-of-range parameters, forcing the codec thread or host process to terminate. No credentials or elevated privileges are required. Repeated exploitation can be used to keep dependent services offline. Verified proof-of-concept material is referenced in the vendor gist and repository sources.

No verified exploit code is available. See the GitHub Gist Code Snippet and the vulnerable GitHub Source Code File for technical details.

Detection Methods for CVE-2025-63095

Indicators of Compromise

Unexpected process termination or Rust panic messages referencing bitstream.rs or write_bits in application logs.
Crash dumps generated by services embedding hello-video-codec 0.1.0 shortly after processing untrusted media input.
Repeated restarts of video processing workers correlated with inbound media uploads or streaming requests.

Detection Strategies

Inventory software builds and Rust Cargo.lock manifests for the tempus-ex:hello-video-codec crate at version 0.1.0.
Enable core dump collection and structured logging on services that decode or transcode user-supplied media.
Correlate application crash events with the network source of the media input to identify potential abuse.

Monitoring Recommendations

Alert on abnormal restart rates for services that link hello-video-codec 0.1.0.
Monitor upstream traffic patterns delivering media payloads to internal codec workers for anomalous file sizes or headers.
Track dependency updates in CI/CD pipelines to flag continued use of the affected crate version.

How to Mitigate CVE-2025-63095

Immediate Actions Required

Identify all applications and services embedding tempus-ex:hello-video-codec 0.1.0 and treat them as exposed until patched.
Restrict media input to trusted sources, and reject unexpected or malformed video containers before they reach the codec.
Isolate codec workers in sandboxed processes so a panic does not disrupt the parent service.

Patch Information

No fixed version has been published in the NVD entry for CVE-2025-63095 at the time of writing. Review the project repository and upstream commits at the GitHub Project Repository for updates, and pin dependencies to a patched revision once released.

Workarounds

Wrap calls to BitstreamWriter::write_bits() in a caller-side validator that enforces safe bit-count and value ranges before invocation.
Run codec processing in a separate process with automatic restart and rate limiting to contain crash impact.
Apply upstream network filtering to drop obviously malformed media before it reaches the vulnerable function.

bash

# Configuration example: audit Cargo dependencies for the affected crate
cargo tree -i hello-video-codec
grep -R "hello-video-codec" ./Cargo.lock
# Remove or upgrade any entry pinned to version 0.1.0 once a fixed release is available