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CVE-2026-7210 is a hash-flooding denial-of-service vulnerability in
Python's XML parsing modules (xml.parsers.expat, xml.etree.ElementTree).
An attacker can craft XML input that forces O(n²) hash collisions in
libexpat's internal name dictionary, causing excessive CPU consumption.
The previous mitigation seeded libexpat's hash function with only 4
bytes of entropy, which is insufficient against a determined attacker.
This patch upgrades to XML_SetHashSalt16Bytes (libexpat >= 2.8.0),
providing a full 16-byte secret. Older expat versions fall back
gracefully to the legacy XML_SetHashSalt via a runtime NULL check.
Backport patch to fix CVE-2026-7210.
https://nvd.nist.gov/vuln/detail/CVE-2026-7210
Upstream fix:
24b8f12544
-- Changes from Upstream --
Replace compile-time version checks with runtime detection of the
XML_SetHashSalt16Bytes function using #pragma weak. This allows using
backported security fixes from expat even when version macros haven't
been bumped (in thus case expat 2.6.4 with CVE-2026-41080).
- Add weak symbol declaration for XML_SetHashSalt16Bytes
- Convert newxmlparseobject() version check to runtime NULL check
- Convert pyexpat_exec() CAPI export check to runtime NULL check
Tested with ptest:
Before: PASSED: 40019, FAILED: 0, SKIPPED: 1882
After: PASSED: 40020, FAILED: 0, SKIPPED: 1882
CVE: CVE-2026-7210
(From OE-Core rev: d753c46085c9d31f3b68d59f863855c909a6f400)
Signed-off-by: Amaury Couderc <amaury.couderc@est.tech>
Signed-off-by: Fabien Thomas <fabien.thomas@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>