PDF_FILTER_CHAIN_UNDECODABLE — Stream advertises a filter that cannot decode the body

medium PDF_FILTER_CHAIN_UNDECODABLE

What it means

PDF stream declares /Filter /FlateDecode but the raw stream bytes are rejected by zlib in both wrapped and raw modes.

Why it fires

A renderer that aborts on the broken stream and one that fails-open see different document content. Targeted samples sometimes deliberately break the filter chain so that lighter-weight scanners skip the stream while heavier renderers still extract a payload from the partial data.

Other PDF heuristics

PDF_LAUNCH_JS_PROTOCOL PDF_LAUNCH_COMMAND PDF_LAUNCH_MSHTA PDF_ADOBE_QR_UNLOCK_LURE PDF_JS_URL_KEYED_READER_EXPLOIT_KIT CVE_2009_2990_U3D_AUTOACTIVATE PDF_ANNOT_AUTHOR_EVAL_STAGER PDF_ANNOT_SUBJECT_HEX_EVAL_STAGER PDF_ANNOT_SUBJECT_MARKER_EVAL_STAGER PDF_JS_BASE_N_TOKEN_DOWNLOADER PDF_BASE64_PE_PAYLOAD PDF_BRAND_INVOICE_LURE_OFFDOMAIN PDF_BRAND_INVOICE_CLOUD_EMAIL_LURE PDF_CORPORATE_PRESENTATION_CLOUD_REDIRECT_LURE PDF_CORRUPTED_FILE_UPDATE_LURE PDF_CRACKED_SOFTWARE_SHORTLINK_LURE PDF_GAME_HACK_SEO_LINK_FARM PDF_DISTRIBUTED_PIRACY_LINK_FARM PDF_DOCUSIGN_DOWNLOAD_LURE PDF_DOCUMENT_ACTION_HOST_MISMATCH_LURE PDF_DYNAMIC_DNS_DOCUMENT_LINK_FARM PDF_SWF_NATIVE_MEMORY_CORRUPTION_PAYLOAD PDF_EMBEDDED_PE_PAYLOAD CVE_2010_1240_EMBEDDED_EXPORT_LAUNCH