<p><strong>TLDR:</strong> A SpaceX engineer’s AI agents found two chained CUPS vulnerabilities that give unauthenticated attackers root file overwrite — no patch yet. A 32-bit overflow in macOS XNU freezes the TCP clock after 49 days of uptime, eventually killing all new TCP connections. FortiClient EMS has a CVSS 9.1 auth bypass under active exploitation with a CISA deadline of April 9. The axios npm package was compromised by North Korean actors and caught in real time by StepSecurity before public disclosure.</p>
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<h2>CUPS chained RCE: unauthenticated root file overwrite, no patch yet</h2>
<p>CVE-2026-34980 and CVE-2026-34990 chain together to give an unauthenticated remote attacker root file overwrite on systems running CUPS 2.4.16 with a shared PostScript queue. The first bug abuses CUPS’ default anonymous print-job policy plus a newline-escaping flaw to get RCE as <code>lp</code>. The second lets a low-privileged user trick the scheduler into leaking a reusable auth token, enabling arbitrary root file writes. No patched release exists yet, though public commits with fixes are available. The researcher noted AI agents are increasingly effective at narrowing vulnerability search spaces — which is either reassuring or alarming depending on who’s running them.</p>
<h2>macOS TCP clock freezes after exactly 49 days</h2>
<p>A 32-bit unsigned integer overflow in XNU’s <code>calculate_tcp_clock()</code> causes <code>tcp_now</code> to freeze permanently once the counter wraps. After that point, TIME_WAIT connections never expire, ephemeral ports exhaust, and no new TCP connections can be established — while ping keeps working fine, which makes this genuinely hard to diagnose. The bug was found on a fleet of long-running Macs monitoring an iMessage service and reproduced live on two machines approaching the overflow threshold. High-risk environments: macOS CI/CD servers, Mac Pro workstations, colocated Mac fleets. The only current workaround is a reboot.</p>
<h2>FortiClient EMS auth bypass under active exploitation, patch by April 9</h2>
<p>CVE-2026-35616 is an improper access control bug in FortiClient EMS 7.4.5 and 7.4.6 with a CVSS of 9.1. Unauthenticated attackers can bypass auth and execute arbitrary code via crafted requests. Exploitation started as quiet, low-volume probing on March 31 before shifting to broader scanning — the classic pattern of someone who found it first and didn’t want to burn it. CISA added it to the KEV catalog with a federal deadline of April 9. This is the second critical, actively exploited FortiClient EMS bug within weeks; both were found by Defused. If you’re running this anywhere, don’t wait for the deadline.</p>
<h2>axios supply chain compromise caught before public disclosure</h2>
<p>Malicious versions of axios (1.14.1 and 0.30.4) — the npm package with 100M+ weekly downloads — contained a hidden dependency installing a remote access trojan that phoned home to a C2 server. A North Korean threat actor (UNC1069/Sapphire Sleet) compromised the maintainer’s machine via social engineering and stole npm and GitHub credentials. StepSecurity’s tooling caught the malicious network behavior in real time before any public disclosure. When they posted GitHub warnings, the attacker deleted them roughly 20 times before GitHub suspended the account. If you installed either version, rotate all credentials immediately.</p>
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<h2>Also notable</h2>
<ul>
<li><strong>GPUBreach (NVIDIA RTX A6000):</strong> University of Toronto researchers chained GDDR6 Rowhammer bit-flips into GPU page table corruption, then escalated to a root shell via NVIDIA driver memory-safety bugs — all without disabling IOMMU. Consumer GPUs without ECC are completely unmitigated. Full details drop April 13 at IEEE S&amp;P.</li>
<li><strong>BlueHammer Windows LPE zero-day:</strong> A disgruntled researcher publicly dropped exploit code for an unpatched Windows TOCTOU + path confusion bug that grants access to the SAM database and SYSTEM privileges. Independent analyst Will Dormann confirmed it works, though it’s not trivially reliable. No Microsoft patch or response yet.</li>
<li><strong>Kubernetes threat activity up 282%:</strong> Unit 42 documents a 282% increase in Kubernetes-related threat actor operations over the past year, with IT sector accounting for 78% of observed activity. Case studies include a North Korean Slow Pisces intrusion using stolen service account tokens and exploitation of CVE-2025-55182 (React Server Components deserialization) within two days of disclosure.</li>
<li><strong>36 malicious npm packages targeting Guardarian:</strong> A threat actor published 36 fake Strapi CMS plugins over 13 hours, with payloads evolving in real time from Redis RCE and container escapes to credential harvesting and PostgreSQL exploitation via hardcoded credentials. Postinstall scripts execute automatically, often with root privileges in CI/CD environments.</li>
<li><strong>Linear security incident post-mortem:</strong> A variable shadowing bug in Linear’s access control layer exposed private team data to unauthorized workspace members for roughly one hour on March 24. About 7,000 client bootstraps were affected. No data left workspaces, no credentials leaked.</li>
<li><strong>MCP reaches Docker-level adoption in 13 weeks:</strong> At the MCP Dev Summit, maintainers from Anthropic, AWS, Microsoft, and OpenAI noted MCP hit Docker-level adoption in 13 weeks versus Docker’s 13 months. Key anti-pattern flagged: naively wrapping 500 API endpoints instead of designing MCP interfaces specifically for agent consumption.</li>
<li><strong>Anthropic Claude Code source map leak:</strong> Anthropic accidentally published a 59.8 MB debug artifact in Claude Code v2.1.88 containing 512,000+ lines of TypeScript source. A researcher extracted the full source within 45 minutes. The leak also revealed unreleased features including a daemon mode called Kairos and an Undercover Mode to strip AI attribution from commits.</li>
<li><strong>Yahoo Japan consolidating 164 OpenStack clusters into one:</strong> LY Corporation is merging LINE’s 4-cluster Verda cloud and Yahoo Japan’s 160+ cluster YNW into a single unified platform called Flava, targeting upstream-aligned code to reduce custom patch burden and ease security upgrades.</li>
<li><strong>Kubernetes AI Conformance program launched:</strong> The new Certified Kubernetes AI Conformance program adds DRA for GPU/TPU control, all-or-nothing scheduling via Kueue, and custom-metric autoscaling for inference workloads on top of standard conformance. GKE and AKS are already adopting it.</li>
<li><strong>Pinterest reduced Spark OOM failures by 96%:</strong> The fix combined improved executor memory observability, adaptive query execution tuning, and Auto Memory Retries that automatically restart failed jobs with increased allocations — rolled out across tens of thousands of daily jobs.</li>
<li><strong>Docker Offload now GA:</strong> Docker’s cloud-hosted engine moves container execution off local machines into isolated, temporary cloud environments over encrypted tunnels, targeting developers on VDI platforms or locked-down laptops. BYOC and GPU-backed instances are on the roadmap.</li>
<li><strong>Post-quantum cryptography urgency shift:</strong> A cryptography engineer argues recent Google and Oratomic papers set a credible 2029 deadline for breaking 256-bit elliptic curves, recommending shipping ML-DSA signatures now and treating non-PQ key exchanges as potential active compromises.</li>
<li><strong>Context rot in LLM agents:</strong> Agent accuracy can drop up to 30% going from 300 to 113k tokens in context. Practical mitigations: hand-crafted minimal tools, progressive disclosure in tool responses, focused system prompts, and routing to specialized sub-agents rather than one bloated agent.</li>
</ul>


Server-side development, system design, API patterns, and distributed architecture.

Backend Digest

A security-focused roundup covering several high-severity vulnerabilities and incidents. Two chained CUPS CVEs allow unauthenticated root file overwrite with no patch yet, discovered via AI-assisted vulnerability hunting. A 32-bit overflow in macOS XNU freezes the TCP clock after 49 days of uptime, killing all new TCP connections with only a reboot as workaround. FortiClient EMS has a CVSS 9.1 auth bypass under active exploitation with a CISA deadline of April 9. The axios npm package (100M+ weekly downloads) was compromised by North Korean actors with malicious versions caught in real time by StepSecurity. Additional items include a GPU Rowhammer attack chain, a Windows LPE zero-day, a 282% rise in Kubernetes threat activity, 36 malicious npm packages, an Anthropic Claude Code source map leak, MCP reaching Docker-level adoption in 13 weeks, and post-quantum cryptography urgency.

CUPS gets chained RCE via AI vuln hunters, macOS TCP clock freezes at 49 days