Merge #1242: Security advisory for CVE-2024-52911

a0f940e Advisory for CVE-2024-52911 (Antoine Poinsot)

Pull request description:

ACKs for top commit:
  fanquake:
    ACK a0f940e
  dergoegge:
    ACK a0f940e

Tree-SHA512: 02bc728b0c2f4b38d7cbc825baaf64ddac41cffaa6321ec1ecd1a80239de9653b62030de3bb58f78db43ed49aeae29d5ec822a657c242599e9a8d72a5eb4a270

Author: fanquake

_posts/en/posts/2026-05-05-disclose-cve-2024-52911.md

@@ -0,0 +1,67 @@
+---
+title: CVE-2024-52911 - Script Interpreter Remote Crash
+name: blog-disclose-cve-2024-52911
+id: en-blog-disclose-cve-2024-52911
+lang: en
+type: advisory
+layout: post
+
+## If this is a new post, reset this counter to 1.
+version: 1
+
+## Only true if release announcement or security annoucement. English posts only
+announcement: 1
+
+excerpt: >
+  A specially-crafted block can be used to remotely crash a Bitcoin Core node by exploiting a use-after-free in its script interpreter.
+---
+
+After Bitcoin Core 0.14.0 and before Bitcoin Core 29.0, validating a specially-crafted block may
+cause the node to access previously freed memory.
+
+During validation, necessary data required for checking inputs for each transaction is
+pre-calculated and cached. For specially crafted invalid blocks, it was possible for this data to be
+destroyed while it was still being accessed by a background validation thread. An attacker capable
+of mining a block with sufficient proof-of-work could have exploited this to crash victim nodes.
+Because of the nature of use-after-free bugs, it is possible that the crash could have been used for
+remote code execution, though constraints on the input (block) data make this unlikely.
+
+This issue is considered **High** severity.
+
+## Details
+
+By default, script validation for new blocks is dispatched to background threads via a vector of
+`CScriptCheck` functors. Each CScriptCheck holds a pointer to a `PrecomputedTransactionData` object
+which stores some data needed by each input in the transaction. Because it stores a pointer and not
+the data itself, care must be taken to ensure that the `PrecomputedTransactionData` outlives the
+`CScriptCheck`.
+
+The script checks lifetime is enforced by an RAII class, `CCheckQueueControl`. However, the control
+is intantiated before the precomputed transaction data. Because local objects in C++ are
+[destructed in reverse order of construction](https://isocpp.org/wiki/faq/dtors#order-dtors-for-locals),
+this means the vector of `PrecomputedTransactionData` is destroyed *before* the
+`CCheckQueueControl`.
+
+This is not an issue when the block is valid, as `CCheckQueueControl::Wait()` will be called before
+the function returns and the `PrecomputedTransactionData` gets destroyed. However, in case of an
+early return (when a separate check fails) a background script thread may read the precomputed
+transaction data after it was destroyed. An attacker could exploit this to crash victim nodes at the
+expense of a valid PoW at tip.
+
+## Attribution
+
+Cory Fields (MIT DCI) discovered this vulnerability and responsibly disclosed it in a detailed
+report containing a proof of concept for reproduction and a proposed mitigation.
+
+## Timeline
+
+- 2024-11-02 Cory Fields privately reports the bug
+- 2024-11-06 Pieter Wuille pushes a covert fix to already open [PR
+  #31112](https://github.com/bitcoin/bitcoin/pull/31112) which works around the issue by removing
+  the early returns
+- 2024-12-03 PR #31112 is merged
+- 2025-04-12 Bitcoin Core version 29.0 is released with a fix
+- 2026-04-19 The last vulnerable Bitcoin Core version (28.x) goes end of life
+- 2026-05-05 Public disclosure.
+
+{% include references.md %}