Fix a potential buffer overflow in the animated PNG decoder when parsing malformed fdAT chunks

F-FLUTTER-APNG-001

Public snapshot: 26 Sep 2026. Status, releases and attribution belong to each source below; none is inferred from another record.

Recorded evidence

—score not recorded

flutter/flutterReported fixflutter/flutter

Fix a potential buffer overflow in the animated PNG decoder when parsing malformed fdAT chunks

fixed publicly

details

Finding IDs: F-FLUTTER-APNG-001
Status: fixed publicly
Reported via: public Flutter PR
Note: merged on 2026-05-21 as commit 9cf97ce9d21d. maintainer note says the fix is based on #184301 and our #183180; it rejects malformed fdAT chunks with data_length below the 4-byte sequence-number minimum. stable cherry-pick #188038 merged to flutter-3.44-candidate.0 on 2026-06-18 as commit a4ce257.

F-FLUTTER-APNG-001: Memory safety. A short APNG fdAT chunk reaches an out-of-bounds access. Reviewed 24 Sep 2026. Mechanism assessed by 1seal.

Mechanism source for F-FLUTTER-APNG-001

Security area (1seal assessment): Memory safety. The APNG decoder rejects fdAT chunks shorter than the four-byte prefix before payload-length arithmetic. Reviewed 21 Sep 2026.

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