CVE-2023-4863: Google Chromium WebP Heap-Based Buffer Overflow Vulnerability

CVE-2023-4863 is a heap-based buffer overflow in Google Chromium's WebP image handling. A remote attacker can trigger an out-of-bounds memory write by supplying a crafted HTML page that causes the WebP codec to process malicious image data. Because many applications embed the Chromium WebP codec, the flaw can reach browsers and other software that decode WebP content. Successful abuse can let an attacker corrupt memory and potentially take control of the process, so teams that run Chromium-based products or any library that reuses the same codec must treat this as a high-priority risk until the vendor update is confirmed and applied.

CISA notes that the vulnerability affects applications that use the WebP codec and requires organizations to apply mitigations according to vendor instructions or to stop using the product if no mitigations exist. Public detail beyond the CWE and the high-level attack path is limited; always verify exact impact and fixed releases against the official vendor advisory.

How it works

The underlying weakness is CWE-787 (Out-of-bounds Write). In a heap-based buffer overflow the program allocates a fixed-size buffer on the heap for WebP decoding, then writes past the end of that buffer when it processes specially crafted image data. The attacker delivers the data inside an HTML page that the vulnerable application renders or parses. Once the write occurs, adjacent heap metadata or objects can be overwritten, which in turn can alter control flow or allow arbitrary code execution inside the process that hosts the WebP codec. No further exploit mechanics are supplied in the public record; defenders should assume a remote, unauthenticated trigger is possible whenever untrusted HTML or WebP content is accepted.

Am I affected? How to find it in your systems

The vulnerable component is the WebP codec shipped with Google Chromium and any third-party application that links or embeds that codec. Typical locations include Chromium-based browsers, Electron applications, desktop clients that render web content, and server-side image-processing pipelines that call the same library.

• Inventory every Chromium-derived browser and every Electron or CEF-based application on endpoints and servers.
• Search package inventories, software bills of materials, and container images for libraries that implement WebP decoding and that are known to pull from Chromium sources.
• Compare installed versions against the fixed releases listed in the vendor advisory; do not rely on version numbers published elsewhere.
• Review crash dumps, browser or application logs, and endpoint-detection telemetry for unexpected process terminations or heap-corruption signatures that coincide with WebP or HTML rendering.
• Where network proxies or web gateways log content types, look for anomalous WebP traffic that precedes process crashes.

If any component cannot be version-checked, treat it as potentially affected until the vendor confirms otherwise.

How to remediate

The primary action is to apply the vendor-supplied update that corrects the WebP heap overflow. Follow the exact remediation steps published in the Chromium or product-specific advisory; CISA's required action is simply to apply those mitigations or to discontinue use if none are available. After patching, restart affected processes and re-verify the installed version. For applications that embed the codec, rebuild or redeploy with the corrected library. Once the update is in place, re-enable any temporary restrictions and confirm that WebP decoding again functions normally under controlled test content.

If you can't patch immediately

Until the official update can be deployed, reduce exposure with compensating controls that limit the attack surface of the WebP codec.

• Segment systems that process untrusted HTML or images so that a compromised process cannot reach high-value assets.
• Apply virtual patching or WAF rules that block or sanitize WebP content and crafted HTML pages known to exercise the decoder; confirm rule efficacy against the vendor's description of the trigger.
• Where the product allows, disable WebP support or force conversion of WebP images to a safer format before they reach the vulnerable codec.
• Increase monitoring for process crashes, heap-corruption alerts, and anomalous outbound connections from browser or image-processing hosts.
• If mitigations remain unavailable, discontinue use of the affected product as directed by CISA until a patch is obtained.

If your data may have been exposed

Actively exploited memory-corruption vulnerabilities can lead to full process compromise and subsequent data theft. If you suspect exploitation, isolate the host, preserve memory and disk images for forensic review, and rotate credentials that may have been accessible to the process. Known ransomware use of this CVE is not documented. As a final hygiene step, you can run a free exposure scan of your email addresses against known breach data sets to determine whether any associated accounts already appear in public dumps.