Apache, urllib3, Chrome Patch Critical Vulnerabilities: What You Need to Know

TL;DR

• Apache HTTP Server patches critical CVE-2025-55753 integer overflow in mod_md, preventing resource exhaustion and ACME renewal denial-of-service
• CVE-2025-66471 in urllib3 allows denial-of-service via compressed response bombs; fix released in v2.6.0 for Python web frameworks and cloud agents
• Critical RCE vulnerability CVE-2025-58098 in Apache HTTP Server's SSI processor enables shell command injection; patch required in 2.4.66 for all affected deployments
• New Windows backdoor NANOR exploits Google Drive API and masquerades as Bitdefender, using XOR-encrypted configs and minidump exfiltration for persistent access
• Zero-day Chrome vulnerability (CVE-2025-466192044) exploited in the wild; patched in Stable Desktop v143.0.7499.109 with potential for remote code execution via renderer flaws

Apache Patches Critical Integer Overflow in mod_md to Prevent ACME Renewal DoS

What vulnerability was patched in Apache HTTP Server?

Apache HTTP Server version 2.4.66, released on December 11, 2025, patches CVE-2025-55753, a critical integer overflow in the mod_md module. The flaw occurred during renewal window calculation for ACME certificate renewals, where a signed 32-bit integer overflow produced negative or excessively large intervals. This triggered unbounded retry loops, consuming CPU resources and causing denial-of-service conditions.

How does the exploit lead to denial-of-service?

The mod_md module, when encountering malformed certificate metadata or extended lifetimes, computed renewal intervals using unsafe arithmetic. Overflow resulted in intervals that caused the module to invoke ACME clients every 12 hours indefinitely. Observed impacts included sustained CPU usage up to 90% and persistent outbound connections to ACME endpoints (5 connections per minute per host), leading to service degradation or complete HTTP outage.

What changes were made in the patch?

The patch introduced:

• Safe arithmetic using apr_uint64_t to prevent integer overflow.
• Clamp logic limiting renewal windows to a maximum of 45% of certificate lifetime.
• Fail-open fallback that disables auto-renewal if calculation fails. These changes eliminate infinite loops while preserving certificate renewal functionality.

Which versions are affected?

All Apache HTTP Server versions from 2.30 to 2.65 are vulnerable. Patched versions include 2.4.66 and later. Back-port patches are available for 2.4.64, 2.3.x, and 2.2.4.

What is the broader security context?

CVE-2025-55753 is the second consecutive mod_md vulnerability (following CVE-2024-55754), indicating systemic issues in ACME integration code. Similar integer overflow fixes have appeared in unrelated projects like KissFFT and wolfSSL, reflecting an industry-wide shift toward safe arithmetic practices. Apache’s 3-month disclosure-to-release cycle is faster than its historical 4–6 months average, aligning with coordinated vendor patch cadences like Microsoft’s Patch Tuesday.

What actions should organizations take?

1. Upgrade to Apache HTTP Server 2.4.66 or apply back-port patches.
2. Set MDRenewMode manual until patched versions are deployed.
3. Implement static analysis to detect unsafe 32-bit arithmetic in certificate-handling modules.
4. Monitor mod_md logs for renewal failures and system CPU usage exceeding 70%.
5. Align internal patch cycles with vendor release windows to reduce exposure time.

urllib3 Compression Bomb Vulnerability CVE-2025-66471 Patched in v2.6.0

What is CVE-2025-66471?

CVE-2025-66471 is a high-severity denial-of-service vulnerability in urllib3 versions 1.0 through 2.5.x. It allows attackers to trigger process crashes by sending highly compressed HTTP responses that expand to gigabytes when decompressed, overwhelming memory and CPU resources.

Which systems are affected?

• Core library: urllib3 1.0–2.5.x
• Web frameworks: Django ≥4.2, Flask ≥2.3, FastAPI, Starlette
• Cloud agents: AWS Lambda, Azure Functions, Google Cloud Run with Python runtimes
• CLI tools: azstd, custom scripts using urllib3 for HTTP calls
• Compression backends: Brotli, Gzip, Zstd, cbrotli

How was the vulnerability fixed?

urllib3 v2.6.0, released on December 5, 2025, introduced:

• A hard limit of 10 MiB per read for decompressed content
• Validation of Content-Length against actual decompressed size
• New exception: urllib3.exceptions.ContentTooLargeError

What actions are required?

1. Upgrade urllib3 to version 2.6.0 or later: pip install --upgrade "urllib3>=2.6.0"
2. Update compression bindings: brotlicffi, brotlipy, zstandard
3. Pin dependencies in requirements.txt or pyproject.toml: urllib3>=2.6.0,<3.0
4. Add exception handling for ContentTooLargeError in application code
5. Monitor for memory spikes and ContentTooLargeError events in observability systems
6. Test downstream libraries (e.g., Kubernetes client, Airflow) for compatibility

What is the broader impact?

This patch also resolves CVE-2025-66418 and CVE-2024-66571, addressing related compression-chain attacks. The fix aligns with industry standards for memory exhaustion defenses. CISA is expected to add this CVE to its Known Exploited Vulnerabilities catalog in Q1 2026. Similar protections are likely to be adopted by other HTTP libraries, including requests, aiohttp, and httpx, in early 2026.

Are there risks in applying the patch?

Some downstream libraries, including Kubernetes client and Airflow, have reported CI failures due to unhandled ContentTooLargeError exceptions. Staged testing in non-production environments is recommended before full deployment.

Apache HTTP Server CVE-2025-58098 Requires Immediate Patching Due to RCE Risk

What is CVE-2025-58098?

CVE-2025-58098 is a critical remote code execution (RCE) vulnerability in Apache HTTP Server versions 2.30 to 2.65. It affects the Server Side Includes (SSI) processor when the #exec cmd="..." directive processes user-controlled query strings, enabling shell command injection.

What systems are affected?

Systems running Apache HTTP Server with SSI enabled and mod_cgid loaded are vulnerable. This includes bare-metal servers, virtual machines, and containerized deployments using default Apache images where SSI is enabled by default. The vulnerability does not affect mod_cgi alone.

What is the impact?

Attackers can execute arbitrary operating system commands remotely, leading to full system compromise. The CVSS v3 score is 8.3, with CVSS v5 scores exceeding 9.0. Impact includes data exfiltration, lateral movement, and service disruption.

Is there a patch?

Yes. Apache HTTP Server version 2.4.66, released on December 1, 2025, includes a fix for CVE-2025-58098. This release also resolves CVE-2025-55753 (mod_md integer overflow), indicating a coordinated hardening effort.

What actions are required?

1. Upgrade all Apache instances to version 2.4.66 or later.
2. Disable SSI functionality using Options -Includes in server configuration if not required.
3. Rebuild container images with the patched Apache binary and SSI disabled.
4. Enforce least-privilege execution for mod_cgid processes (non-root user, restricted filesystem access).
5. Implement network monitoring for #exec command patterns using IDS/IPS rules.
6. Audit container registries for vulnerable Apache images using tools like Trivy or Clair.

What broader trends does this reflect?

This vulnerability aligns with a 2025 pattern of server-side parsing flaws across Apache ecosystems (e.g., Tika, Tomcat) and industry-wide batch remediation. The bundling of unrelated fixes in a single release reduces operational overhead. Default-enabled features in container images continue to serve as a major supply-chain exposure vector.

What is the expected next step?

CISA is likely to add CVE-2025-58098 to its Known Exploited Vulnerabilities (KEV) catalog within 30 days, triggering mandatory remediation deadlines for federal agencies and regulated sectors. Automated scanning for #exec patterns has already begun in threat actor networks.

Chrome Zero-Day Exploited via Renderer Flaw; Patch Released in Version 143.0.7499.109

What is the nature of CVE-2025-466192044?

A zero-day vulnerability in Google Chrome’s renderer process allows remote code execution through memory corruption flaws. Exploitation occurs when a user visits a malicious website that triggers the flaw, enabling attackers to execute arbitrary code on the host system.

When was the vulnerability patched?

• Patch release date: December 10, 2025
• Affected version: Chrome Stable Desktop prior to 143.0.7499.109
• Fixed version: 143.0.7499.109

Which systems are at risk?

• All desktop platforms running Chrome versions before 143.0.7499.109
• Systems with automatic updates disabled
• Enterprise environments using legacy deployment pipelines

What is the exploitation status?

• Actively exploited in the wild as of December 9, 2025
• No public exploit code has been released
• Attack vectors include malicious advertisements and compromised web domains

What are the recommended actions?

1. Update Chrome to version 143.0.7499.109 or later
2. Enable automatic updates for all endpoints
3. Deploy endpoint detection and response (EDR) tools to monitor for renderer process anomalies
4. Restrict execution of untrusted scripts via content security policies (CSP)
5. Audit browser extension usage for unauthorized permissions

How does this relate to broader trends?

This vulnerability aligns with the 2025 trend of renderer-based exploits in web browsers, mirroring prior incidents in Firefox and Safari. The use of memory corruption in rendering engines remains a high-yield attack vector due to the complexity of modern JavaScript and WebAssembly execution environments. Patch deployment timelines remain critical, as exploitation begins within hours of public disclosure.

What is the impact of delayed patching?

Organizations with delayed update cycles face elevated risk of compromise. Unpatched systems are vulnerable to credential theft, lateral movement, and malware deployment. Enterprise environments using managed browsers must verify patch compliance across all endpoints.

Are there alternative mitigations?

• Disable JavaScript in high-risk browsing contexts
• Use sandboxed browsing environments for untrusted sites
• Employ browser isolation technologies for sensitive operations

No known workarounds exist that fully mitigate the flaw without updating the browser.