CVE-2026-91826: Samsung rLottie Buffer Overflow Vulnerability

CVE-2026-91826 Overview

CVE-2026-91826 is a stack-based buffer overflow [CWE-121] in Samsung's open source rLottie library. The flaw affects rLottie commit 480a2ad0c5d2e45458c545b8213279e9e8b71e39. Attackers can trigger memory corruption by supplying crafted vector animation files to an application that uses the library for rendering. Exploitation requires local access and user interaction, such as opening or previewing a malicious animation. rLottie is used to decode and render Lottie JSON animations across desktop, mobile, and embedded applications, which broadens the exposure surface.

Critical Impact
Rendering a crafted Lottie animation can corrupt stack memory in the host process, causing crashes or altering program state during animation parsing.

Affected Products

Samsung rLottie library at commit 480a2ad0c5d2e45458c545b8213279e9e8b71e39
Applications embedding the affected rLottie build for animation rendering
Downstream projects consuming rLottie as a dependency for Lottie playback

Discovery Timeline

2026-09-15 - CVE-2026-91826 published to NVD
2026-09-15 - Last updated in NVD database

Technical Details for CVE-2026-91826

Vulnerability Analysis

rLottie parses Lottie JSON animation definitions and renders vector graphics frames at runtime. The vulnerability is a stack-based buffer overflow that occurs during rendering of attacker-controlled vector animation content. When rLottie processes a malformed animation, data written to a fixed-size stack buffer exceeds its allocation, overwriting adjacent stack memory. This corruption can crash the calling process and, depending on compiler mitigations and buffer layout, influence control flow within the rendering thread. The issue is reachable through any application that loads untrusted Lottie files, which extends the impact beyond the library itself. For additional context, see the GitHub Pull Request Discussion.

Root Cause

The root cause is missing or insufficient bounds validation on data derived from a Lottie animation before it is written into a stack-allocated buffer inside the rendering path. Trusting attacker-controlled sizes or indices during parsing leads to the classic [CWE-121] stack overflow condition.

Attack Vector

An attacker crafts a malicious Lottie animation and delivers it to a target user through a file, message, or bundled asset. The victim opens or previews the animation in an application that uses the affected rLottie build. Rendering triggers the overflow. Attack complexity is low, no privileges are required, but user interaction is needed, consistent with the local attack vector.

No verified public proof of concept is available. See the GitHub Pull Request Discussion for technical detail on the parsing path.

Detection Methods for CVE-2026-91826

Indicators of Compromise

Unexpected crashes or stack corruption reports in processes that load rLottie, particularly when opening .json or .lottie animation files.
Presence of Lottie animation files from untrusted sources in user download, temp, or messaging cache directories.
Application telemetry showing abnormal termination during animation frame rendering.

Detection Strategies

Inventory software that embeds rLottie and identify builds at or derived from commit 480a2ad0c5d2e45458c545b8213279e9e8b71e39.
Enable AddressSanitizer or equivalent memory instrumentation in test builds to surface overflow during Lottie file fuzzing.
Hunt for process crash events correlated with recent Lottie file access in endpoint telemetry.

Monitoring Recommendations

Monitor endpoint crash dumps for stack corruption signatures in rLottie symbols or animation rendering threads.
Track file writes of Lottie JSON assets originating from browsers, chat clients, and email attachments.
Alert on repeated crashes of the same user-mode process shortly after opening media files.

How to Mitigate CVE-2026-91826

Immediate Actions Required

Identify applications using the vulnerable rLottie commit and restrict them from opening Lottie files from untrusted sources.
Update rLottie to a build that includes the fix referenced in the upstream pull request.
Rebuild and redistribute downstream applications that statically link the library.

Patch Information

Remediation is tracked upstream through the GitHub Pull Request Discussion. Integrators should pull a commit that supersedes 480a2ad0c5d2e45458c545b8213279e9e8b71e39 and incorporates the bounds-checking fix, then rebuild dependent binaries.

Workarounds

Block or filter Lottie animation files delivered from untrusted channels at email and web gateways.
Disable in-app previews of animation attachments in vulnerable applications until patched.
Ensure compiler mitigations such as stack canaries, ASLR, and non-executable stacks are enabled in builds that link rLottie.

bash

# Configuration example
# Rebuild rLottie from a patched commit
git clone https://github.com/Samsung/rlottie.git
cd rlottie
git checkout <patched-commit-sha>
mkdir build && cd build
cmake .. -DCMAKE_C_FLAGS="-fstack-protector-strong -D_FORTIFY_SOURCE=2" \
         -DCMAKE_CXX_FLAGS="-fstack-protector-strong -D_FORTIFY_SOURCE=2"
cmake --build . --config Release