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How CVE-2026-17760 Works
CVE-2026-17760 is a side-channel information disclosure vulnerability residing in Google Chrome’s NoStatePrefetch component, affecting all versions prior to 151.0.7922.72. NoStatePrefetch is a background navigation mechanism introduced by Chrome to replace the deprecated prerendering process; it is used to implement various APIs and features, including the Resource Hints API and address bar page preloading. Unlike full prerendering, NoStatePrefetch consumes significantly less memory while still reducing page load times by fetching resources in advance.
The vulnerability stems from improper protection against physical side channels, classified under CWE-1300. Specifically, the NoStatePrefetch component does not contain sufficient safeguards to prevent information leakage through observable timing differences, cache states, or other microarchitectural side effects during speculative resource fetching. A remote attacker can exploit this flaw by crafting a malicious HTML page that, when loaded by a victim, triggers NoStatePrefetch requests to cross-origin resources. By carefully measuring the timing or cache footprint of these prefetch operations, the attacker can infer sensitive information about the victim’s cross-origin data—such as whether specific resources exist, their size, or even partial content—without the victim’s explicit knowledge or consent.
The attack requires no authentication and can be launched remotely over the network. However, it does require user interaction: the victim must visit the attacker-controlled page. The attack complexity is considered low, meaning that a reasonably skilled attacker can reliably reproduce the side-channel measurements. The vulnerability is not known to be exploited in the wild as of publication, and no public technical details or exploit code have been released. The Chromium security team assigned this issue a Medium severity rating.
The flaw was addressed in Chrome 151.0.7922.72 by implementing additional isolation and noise-injection mechanisms within the NoStatePrefetch engine to prevent cross-origin data from being inferred through side channels. Google credits internal discovery for this vulnerability, part of a broader security sweep that patched 370 vulnerabilities across the Chrome 151 release.
DailyCVE Form
Platform: Google Chrome
Version: < 151.0.7922.72
Vulnerability: Side-channel info leak
Severity: Medium (CVSS 4.3)
Date: 2026-07-30
Prediction: Patch already available
What Undercode Say: Analytics & Detection
Analytics Overview:
This vulnerability is detectable through timing analysis and cache-state monitoring. Security analysts can use the following approaches to identify potential exploitation attempts:
1. Browser Histogram Monitoring (Chrome Internal Metrics):
Chrome exposes NoStatePrefetch usage statistics via internal histograms. Abnormal prefetch activity patterns may indicate side-channel probing:
Access Chrome histograms for NoStatePrefetch (via chrome://histograms) Look for unusual spikes in: - "NoStatePrefetch.Abandoned" – prefetch requests cancelled mid-flight - "NoStatePrefetch.Usage" – frequency of prefetch triggers - "NoStatePrefetch.TimeToFirstContentfulPaint" – timing anomalies
2. Network Traffic Analysis:
Monitor for unexpected cross-origin prefetch requests originating from a single page:
Using tcpdump to capture Chrome prefetch traffic (port 443 for HTTPS) sudo tcpdump -i any -s 0 -A 'tcp port 443' | grep -i "prefetch" Using Wireshark display filter for HTTP/2 PUSH_PROMISE or prefetch headers http2.headers.method == "GET" && http2.headers.path contains "prefetch"
3. JavaScript Timing Probe Detection (Client-Side):
Attackers often use `performance.now()` or `performance.getEntries()` to measure resource load times. The following script can be injected to detect anomalous timing measurements:
// Monitor for excessive performance API usage (potential side-channel probe)
const origNow = performance.now.bind(performance);
let probeCount = 0;
performance.now = function() {
probeCount++;
if (probeCount > 1000) {
console.warn("[CVE-2026-17760 Detection] Excessive timing probes detected!");
}
return origNow();
};
4. Chrome Enterprise Policy Enforcement:
Administrators can disable NoStatePrefetch entirely via Group Policy to mitigate risk:
Windows Registry – Disable NoStatePrefetch
reg add "HKLM\Software\Policies\Google\Chrome" /v NoStatePrefetchEnabled /t REG_DWORD /d 0 /f
macOS – using defaults command
defaults write com.google.Chrome NoStatePrefetchEnabled -bool false
Linux – via policies.json
echo '{"NoStatePrefetchEnabled": false}' > /etc/opt/chrome/policies/managed/no_prefetch.json
Exploit
As of the current analysis, no public exploit code exists for CVE-2026-17760. The vulnerability is considered theoretical and requires significant reverse-engineering effort to weaponize. However, a hypothetical exploit would follow this pattern:
Hypothetical Attack Flow:
- Attacker hosts a malicious HTML page containing hidden iframes or resource links pointing to cross-origin targets (e.g., `https://bank.com/account-balance`).
- Victim visits the page – the attacker’s JavaScript triggers NoStatePrefetch for these cross-origin URLs using the Resource Hints API or similar mechanisms.
- Side-channel measurement – the attacker’s script repeatedly measures the time taken for prefetch responses or observes cache behavior using `performance.now()` and
performance.getEntriesByType('resource'). - Data inference – by comparing timing patterns against a known baseline, the attacker deduces whether specific resources exist, their approximate size, or other metadata – effectively leaking cross-origin information.
Example POC Snippet (Illustrative – Not Functional):
<!DOCTYPE html> <html> <head> <link rel="prefetch" href="https://victim.com/sensitive-data" as="document"> </head> <body> <script> // Hypothetical side-channel measurement loop const targets = [ 'https://bank.com/account', 'https://bank.com/balance', 'https://bank.com/transactions' ]; function measurePrefetch(url) { const start = performance.now(); fetch(url, { mode: 'no-cors', cache: 'force-cache' }); return performance.now() - start; } // Repeated measurements to infer existence of resources targets.forEach(url => { const avgTime = Array.from({ length: 50 }, () => measurePrefetch(url)) .reduce((a,b) => a+b, 0) / 50; console.log(<code>${url}: ${avgTime}ms</code>); }); </script> </body> </html>Exploit Market Value:
Current exploit price estimates range from $5,000 to $25,000 on underground markets. The CTI Interest Score is relatively low (1.36 out of 10), indicating limited attacker focus as of July 2026.
Protection
1. Upgrade to Chrome 151.0.7922.72 or Later
This is the definitive fix. Google released the patched version on July 30, 2026. Users should update immediately:
Windows – Check for updates via Chrome menu or CLI "C:\Program Files\Google\Chrome\Application\chrome.exe" --version Expected output: Google Chrome 151.0.7922.72 or higher macOS – via terminal /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome --version Linux – via package manager google-chrome --version Or update using apt/yum/dnf sudo apt update && sudo apt install google-chrome-stable
2. Disable NoStatePrefetch via Enterprise Policy
For organizations unable to immediately upgrade, disabling the component provides a temporary mitigation:
// policies.json (Linux/Windows managed) { "NoStatePrefetchEnabled": false }3. Browser Hardening
– Enable Site Isolation (chrome://flags/enable-site-per-process) to limit cross-origin data exposure.
– Disable third-party cookies and use Enhanced Tracking Protection.
– Consider using extension-based request blockers (e.g., uBlock Origin) to prevent unwanted prefetch requests.
4. Network-Level Controls
– Deploy Content Security Policy (CSP) with `prefetch-src ‘none’` to restrict prefetch origins.
– Implement Subresource Integrity (SRI) to detect tampered resources.
5. User Awareness
– Educate users to avoid visiting untrusted websites and to keep browsers auto-updated.
– Encourage use of Chrome’s Safe Browsing feature, which blocks known malicious pages.
Impact
Confidentiality Impact:
Low – The vulnerability allows leakage of cross-origin data, but only metadata such as resource existence, size, or timing patterns, not full content. An attacker cannot directly read sensitive user data like passwords or session tokens, but can infer state information (e.g., whether a user is logged into a specific service).
Integrity Impact:
None – The vulnerability does not allow modification of any data.
Availability Impact:
None – The vulnerability does not cause crashes, denial of service, or performance degradation.
Scope:
Unchanged – The attack does not escalate privileges or affect resources beyond the victim’s session.
CVSS v3.1 Base Score: 4.3 (Medium) –
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N.
Real-World Risk:
While the CVSS score is moderate, the practical risk is elevated due to the low attack complexity and no authentication requirement. An attacker could silently probe a victim’s browsing context to map active sessions, detect logged-in services, or infer browsing history. This information could be chained with other vulnerabilities to launch more sophisticated attacks, such as targeted phishing or session fixation.
Patch Urgency:
Given that a patch is already available and no active exploits are known, the urgency is moderate. However, enterprises handling sensitive data should prioritize updating to avoid potential data leakage, especially in environments where cross-origin information is highly confidential (e.g., financial, healthcare, government sectors).
Long-Term Implications:
This CVE highlights the inherent risks of speculative prefetching mechanisms in modern browsers. Even with memory-efficient designs like NoStatePrefetch, side-channel leakage remains a persistent challenge. Future browser versions will likely incorporate stronger isolation primitives and noise injection to mitigate such threats, but developers must remain vigilant when implementing performance optimizations that involve cross-origin resource loading.
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Sources:
Reported By: nvd.nist.gov
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