CVE-2021-21149 Overview
CVE-2021-21149 is a stack buffer overflow vulnerability in the Data Transfer component of Google Chrome on Linux. Versions prior to 88.0.4324.182 allow a remote attacker to trigger out-of-bounds memory access by serving a crafted HTML page. The flaw is categorized as an out-of-bounds write [CWE-787] and affects Chrome installations on Linux distributions including Fedora 32 and Fedora 33.
Successful exploitation requires user interaction, typically visiting a malicious website. The vulnerability impacts confidentiality, integrity, and availability of the affected system.
Critical Impact
A remote attacker can perform out-of-bounds memory access in the Chrome renderer process via a crafted HTML page, potentially leading to memory corruption and sandbox-constrained code execution on Linux hosts.
Affected Products
- Google Chrome on Linux prior to 88.0.4324.182
- Fedora 32
- Fedora 33
Discovery Timeline
- 2021-02-22 - CVE-2021-21149 published to the National Vulnerability Database
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2021-21149
Vulnerability Analysis
The vulnerability resides in the Data Transfer subsystem of Google Chrome on Linux. The Data Transfer component handles clipboard and drag-and-drop operations exposed to web content through the DataTransfer interface. A stack buffer overflow occurs when input from a crafted HTML page exceeds the bounds of a fixed-size stack buffer during processing.
The attack vector is network-based and requires user interaction such as visiting a malicious page. The flaw allows out-of-bounds memory access that can corrupt adjacent stack data, including saved return addresses and frame pointers within the renderer process.
Memory corruption in browser components is commonly chained with sandbox escapes to achieve full code execution. While Chrome's renderer sandbox limits direct system impact, attackers can use overflows of this class to leak memory, bypass mitigations such as Address Space Layout Randomization (ASLR), or pivot toward further exploitation.
Root Cause
The root cause is improper bounds checking when writing data to a stack-allocated buffer in the Data Transfer code path. The CWE classification [CWE-787] indicates an out-of-bounds write where the program writes past the end of the intended buffer. The exact source-level details are tracked in the upstream Chromium Bug Report #1138143, which remains access-restricted.
Attack Vector
Exploitation requires the victim to load attacker-controlled HTML content in a vulnerable Chrome build on Linux. The crafted page drives Data Transfer operations that overflow the stack buffer. No prior authentication or elevated privileges are needed on the target system. The vulnerability mechanism is described in the Google Chrome Update Announcement; no public proof-of-concept exploit is available.
Detection Methods for CVE-2021-21149
Indicators of Compromise
- Chrome renderer process crashes or unexpected terminations on Linux endpoints, particularly with stack corruption signatures such as SIGSEGV in chrome followed by canary or return-address violations.
- Chrome binaries on Linux reporting versions earlier than 88.0.4324.182 in software inventory data.
- Outbound connections from Chrome to recently registered or low-reputation domains hosting HTML payloads that interact with clipboard or drag-and-drop APIs.
Detection Strategies
- Inventory installed Chrome versions across Linux fleets and flag any host running a build below 88.0.4324.182.
- Monitor for repeated Chrome renderer crashes in /var/log/ and systemd journal entries that may indicate exploitation attempts.
- Correlate browser process anomalies with proxy or DNS telemetry to identify suspicious page loads preceding crashes.
Monitoring Recommendations
- Ingest endpoint process, crash, and network telemetry into a centralized data lake for retrospective hunting against browser exploitation patterns.
- Track Fedora and other Linux package management events to confirm installation of patched chromium builds referenced in the Gentoo GLSA 202104-08 and Fedora advisories.
- Alert on Chrome child processes spawning unexpected shells, interpreters, or persistence mechanisms.
How to Mitigate CVE-2021-21149
Immediate Actions Required
- Update Google Chrome on all Linux endpoints to version 88.0.4324.182 or later as specified in the Google Chrome Update Announcement.
- Apply distribution-specific updates, including the Fedora package updates announced in Fedora Package Announcement BI6ZIJQYP5DFMYVX4J5OGOU2NQLEZ3SB and Fedora Package Announcement FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX.
- Restart Chrome processes after update to ensure the patched binary is loaded into memory.
Patch Information
Google released Chrome 88.0.4324.182 for the Stable channel to address this issue along with other security fixes. Gentoo published GLSA 202104-08 covering the corresponding chromium ebuild. Fedora 32 and Fedora 33 received patched chromium packages through the standard dnf update channel.
Workarounds
- Restrict browsing to trusted sites and block known malicious domains at the network egress layer until patching is complete.
- Enforce Chrome enterprise policies that disable unnecessary clipboard and drag-and-drop integrations where feasible.
- Use distribution package managers to verify and pin Chrome or Chromium to fixed versions across managed Linux hosts.
# Configuration example
# Fedora: update chromium to the patched build
sudo dnf upgrade --refresh chromium
# Verify the installed Chrome/Chromium version is 88.0.4324.182 or later
google-chrome --version
chromium-browser --version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
