[3.12] gh-133767: Fix use-after-free in the unicode-escape decoder with an error handler (GH-129648) (GH-133944) #134337
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…der with an error handler (pythonGH-129648) (pythonGH-133944) If the error handler is used, a new bytes object is created to set as the object attribute of UnicodeDecodeError, and that bytes object then replaces the original data. A pointer to the decoded data will became invalid after destroying that temporary bytes object. So we need other way to return the first invalid escape from _PyUnicode_DecodeUnicodeEscapeInternal(). _PyBytes_DecodeEscape() does not have such issue, because it does not use the error handlers registry, but it should be changed for compatibility with _PyUnicode_DecodeUnicodeEscapeInternal(). (cherry picked from commit 9f69a58) (cherry picked from commit 6279eb8) Co-authored-by: Serhiy Storchaka <[email protected]>
This was referenced May 20, 2025
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Reference: python/cpython#134337 PR: 287009
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Reference: python/cpython#134337 PR: 287009
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## Summary Fix use-after-free vulnerability in the unicode-escape decoder with non-strict error handlers. ## Details - **CVE**: CVE-2025-4516 - **Severity**: Medium - **Issue**: Use-after-free crash when using `bytes.decode("unicode_escape", error="ignore|replace")` ## Changes - Add CVE-2025-4516.patch from upstream merged PRs - Python 3.12: [PR #134337](python/cpython#134337) - Python 3.13: [PR #133944](python/cpython#133944) - Increment epoch to 2 for both packages ## Status - ✅ Python 3.12: Upstream patch merged and applied - ✅ Python 3.13: Upstream patch merged and applied - ⏳ Python 3.9, 3.10, 3.11: Waiting for upstream PRs to be merged ## Testing CI will validate that: - Patches apply cleanly - Packages build successfully - Tests pass ## References - [CVE-2025-4516 Details](https://www.cve.org/CVERecord?id=CVE-2025-4516) - [Security Advisory](https://mail.python.org/archives/list/[email protected]/thread/L75IPBBTSCYEF56I2M4KIW353BB3AY74/) - Related to: chainguard-dev/internal-dev#12589
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Pull request: python/cpython#134337 Commit: python/cpython@a75953b Branch history: https://github.com/python/cpython/commits/3.12/ Commit is included in the 3.12.11 release per 3.12 branch history
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If the error handler is used, a new bytes object is created to set as the object attribute of UnicodeDecodeError, and that bytes object then replaces the original data. A pointer to the decoded data will became invalid after destroying that temporary bytes object. So we need other way to return the first invalid escape from _PyUnicode_DecodeUnicodeEscapeInternal().
_PyBytes_DecodeEscape() does not have such issue, because it does not use the error handlers registry, but it should be changed for compatibility with _PyUnicode_DecodeUnicodeEscapeInternal().
(cherry picked from commit 9f69a58) (cherry picked from commit 6279eb8)
unicode_escapedecoder with error handler #133767