Show HN: CVE-2026-40369 Windows Kernel Arbitrary Write Chrome SBX
A researcher aimed to exploit a Windows kernel bug to escape Chrome's renderer sandbox for the Pwn2Own Berlin 2026 competition. Despite developing a successful exploit, the researcher was rejected from the contest due to overwhelming interest and capacity limits. Consequently, the researcher has opted for full public disclosure of the findings.
- ▪The researcher targeted a Windows kernel bug to escape Chrome's renderer sandbox.
- ▪They discovered a trivially exploitable arbitrary kernel write primitive in a heavily audited syscall.
- ▪The researcher was rejected from the Pwn2Own Berlin competition due to maximum capacity limits.
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Story provenance
Source · retrieval · rights · ranking — open for full record
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Attribution is not the same as permission. This drawer separates discovery metadata, excerpts, WeSearch-generated summaries, reuse status, and whether the publisher receives the visit. Nothing here claims a legal grant the publisher has not made.
Record
| Original publisher | Pwn2nimron |
| Canonical URL | https://pwn2nimron.com/blog |
| Publication time | Thu, 28 May 2026 21:13:13 +0000 |
| Retrieval time | 2026-05-28T21:29:38.368Z |
| Last seen | 2026-05-28T21:29:38.368Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | Nqx91fhcYFNs |
| Cluster logic | Grouped by semantic title/content similarity across sources within a rolling window. Same-publisher template collisions are excluded from coverage comparison. |
| Ranking reason | Story pages are not engagement-ranked. Hub feeds use recency, with optional source-diversified chronological ordering (cap consecutive stories per source). No personalized ranking. |
| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
Rights status (four layers)
WeSearch handling by dimension
| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
Preface — How I Got Here I wanted to compete in Pwn2Own Berlin 2026 in the Web Browser category. The target: escape Chrome's renderer sandbox via a Windows kernel bug — starting from a compromised renderer process, demonstrate code execution outside the sandbox. Chrome's sandbox makes the kernel attack surface surprisingly small. The renderer process runs at untrusted integrity with a heavily restricted token. Win32k is completely locked out (win32k lockdown), which eliminates the entire GDI/USER attack surface that has historically been the bread and butter of Windows kernel exploitation. What's left? A handful of NT syscalls that aren't blocked: file operations (heavily filtered by the broker), registry (mostly read-only), and a few system information queries.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Pwn2nimron.
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