Versions & Functionality Levels (FLEVELs)

The Functionality Level (or FLEVEL) is an integer that signatures may use to define which versions of ClamAV the signature features support. It is up to the signature writers to select the correct FLEVEL or range of FLEVELs when writing a signature so that it does not cause failures in older versions of ClamAV.

Setting appropriate FLEVELs in signatures is particularly crucial when using features added in the last 3-4 major release versions.

ClamAV Version to FLEVEL chart

Release DateReleaseFLEVELFunctionalityLevel (bytecode enum)clamav lib.sofreshclam lib.soAPI/ABI changes, major features, other notes
n/a1.5.0220FUNC_LEVEL_1_5n/an/an/an/a
Sep-20241.4.1211FUNC_LEVEL_1_4_112:03:0012.0.33:02:003.0.2Critical bug fixes
Sep-20241.3.2202FUNC_LEVEL_1_3_212:02:0012.0.23:01:003.0.1Critical bug fixes
Sep-20241.0.7167FUNC_LEVEL_1_0_711:00:0011.0.02:02:002.0.2Critical bug fixes
Sep-20240.103.12133FUNC_LEVEL_0103_129:05:009.0.52:01:002.0.1Critical bug fixes
Aug-20241.4.0210FUNC_LEVEL_1_412:03:0012.0.33:02:003.0.2ALZ (CL_TYPE_ALZ) and LHA/LZH (CL_TYPE_LHA_LZH) archives archive extraction. Options to disable image fuzzy hashing.
Apr-20241.3.1201FUNC_LEVEL_1_3_112:02:0012.0.23:01:003.0.1Critical bug fixes
Apr-20241.2.3193FUNC_LEVEL_1_2_312:01:0012.0.13:01:003.0.1Critical bug fixes
Feb-20241.0.6166FUNC_LEVEL_1_0_611:00:0011.0.02:02:002.0.2Critical bug fixes
Feb-20241.3.0200FUNC_LEVEL_1_312:02:0012.0.23:01:003.0.1OneNote attachment extraction (CL_TYPE_ONENOTE); CL_TYPE_PYTHON_COMPILED (.pyc) file type recognition.
Feb-20241.2.2192FUNC_LEVEL_1_2_212:01:0012.0.13:01:003.0.1Critical bug fixes
Feb-20241.0.5165FUNC_LEVEL_1_0_511:00:0011.0.02:02:002.0.2Critical bug fixes
Oct-20231.2.1191FUNC_LEVEL_1_2_112:01:0012.0.13:01:003.0.1Critical bug fixes
Oct-20231.1.3183FUNC_LEVEL_1_1_312:00:0012.0.03:00:003.0.0Critical bug fixes
Oct-20231.0.4164FUNC_LEVEL_1_0_411:00:0011.0.02:02:002.0.2Critical bug fixes
Oct-20230.103.11132FUNC_LEVEL_0103_119:05:009.0.52:01:002.0.1Critical bug fixes
Aug-20231.2.0190FUNC_LEVEL_1_212:01:0012.0.13:01:003.0.1UDF partition support
Aug-20231.1.2182FUNC_LEVEL_1_1_212:00:0012.0.03:00:003.0.0Upgrade UnRAR library for security fix
Aug-20231.0.3163FUNC_LEVEL_1_0_311:00:0011.0.02:02:002.0.2Upgrade UnRAR library for security fix
Aug-20230.103.10131FUNC_LEVEL_0103_109:05:009.0.52:01:002.0.1Upgrade UnRAR library for security fix
Aug-20231.1.1181FUNC_LEVEL_1_1_112:00:0012.0.03:00:003.0.0Critical bug fixes; Fix build issue with Rust 1.70+; Fix build issue with openssl 3 on macOS
Aug-20231.0.2162FUNC_LEVEL_1_0_211:00:0011.0.02:02:002.0.2Critical bug fixes; Fix build issue with Rust 1.70+; Fix build issue with openssl 3 on macOS
Aug-20230.103.9130FUNC_LEVEL_0103_99:05:009.0.52:01:002.0.1Critical bug fixes
May-20231.1.0180FUNC_LEVEL_1_112:00:0012.0.03:00:003.0.0Added cl_cvdgetage() and cl_engine_set_clcb_vba() functions.
Feb-20231.0.1161FUNC_LEVEL_1_0_111:00:0011.0.02:02:002.0.2Critical bug fixes; Fix an allmatch detection issue with the preclass bytecode hook.
Feb-20230.105.2152FUNC_LEVEL_0105_210:00:019.1.02:02:002.0.2Critical bug fixes; Fixed an issue loading Yara rules containing regex strings with an escaped forward-slash (/) followed by a colon (:).
Feb-20230.103.8129FUNC_LEVEL_0103_89:05:009.0.52:01:002.0.1Critical bug fixes
Nov-20221.0.0160FUNC_LEVEL_1_011:00:0011.0.02:02:002.0.2Added cl_cvdunpack() API. Added unstable clcb_file_inspection callback, and cl_engine_set_clcb_file_inspection() API. All-match mode is now more reliable. Fix logical signature "Intermediates" feature.
May-20220.105.1151FUNC_LEVEL_0105_110:00:019.1.02:02:002.0.2Fix logical signature "Intermediates" feature.
May-20220.105.0150FUNC_LEVEL_010510:00:019.1.02:02:002.0.2Fuzzy image hash subsignatures; Fix byte-compare subsignature premature alert
Nov-20210.104.4144FUNC_LEVEL_0104_410:00:019.1.02:02:002.0.2Fix logical signature "Intermediates" feature.
Nov-20210.104.3143FUNC_LEVEL_0104_310:00:019.1.02:02:002.0.2Critical bug fixes; Fix byte-compare subsignature premature alert (0.104)
Nov-20210.104.2142FUNC_LEVEL_0104_210:00:019.1.02:02:002.0.2Critical bug fixes
Nov-20210.104.1141FUNC_LEVEL_0104_110:00:019.1.02:02:002.0.2Critical bug fixes
Nov-20210.103.7128FUNC_LEVEL_0103_89:05:009.0.52:01:002.0.1Fix logical signature "Intermediates" feature.
Nov-20210.103.6127FUNC_LEVEL_0103_69:05:009.0.52:01:002.0.1Critical bug fixes; Fix byte-compare subsignature premature alert (0.103)
Nov-20210.103.5126FUNC_LEVEL_0103_59:05:009.0.52:01:002.0.1Critical bug fixes
Nov-20210.103.4125FUNC_LEVEL_0103_49:05:009.0.52:01:002.0.1Critical bug fixes
Sep-20210.104.0140FUNC_LEVEL_010410:00:019.1.02:02:002.0.2CMake stabilized (autotools removed); Added db load/compile/free callbacks to clamav.h API.
Jun-20210.103.3124FUNC_LEVEL_0103_39:05:009.0.52:01:002.0.1Critical bug fixes
May-20210.103.2123FUNC_LEVEL_0103_29:05:009.0.52:01:002.0.1Security fixes
Feb-20210.103.1122FUNC_LEVEL_0103_19:05:009.0.52:01:002.0.1Fix PNG parser; Loosen GIF format validation (trailer byte); Fix scan issue on Windows RAM disks; Fix clamonacc FD-passing; Enable JPEG & TIFF validation; Add CL_TYPE_JPEG, CL_TYPE_TIFF; Adds ALERT_BROKEN_IMAGES scan heuristics option
Sep-20200.103.0120FUNC_LEVEL_01039:05:009.0.52:01:002.0.1Add CL_TYPE_PNG, CL_TYPE_GIF; Add XLM macro detection; Add bzip2 & LZMA decompression functions to bytecode API
Jul-20200.102.4115FUNC_LEVEL_0102_49:04:009.0.42:00:002.0.0Security fixes
May-20200.102.3114FUNC_LEVEL_0102_39:04:009.0.42:00:002.0.0Security fixes
Feb-20200.102.2113FUNC_LEVEL_0102_29:04:009.0.42:00:002.0.0Security fixes
Nov-20190.102.1112FUNC_LEVEL_0102_19:04:009.0.42:00:002.0.0Security fixes; Significant load time improvement for LDBs with common pattern prefixes
Nov-20190.101.5106FUNC_LEVEL_0101_59:04:009.0.4Security fixes; Significant load time improvement for LDBs with common pattern prefixes
Oct-20190.102.0110FUNC_LEVEL_01029:04:009.0.42:00:002.0.0BytecodeKind: BC_ELF_UNPACKER, BC_MACHO_UNPACKER; Add CL_TYPE_EGG/CL_TYPE_EGG_SFX; Added scan time limit
Aug-20190.101.4105FUNC_LEVEL_0101_49:04:009.0.4Security fixes; Added scan time limit, bzip vuln fix
Aug-20190.101.3102FUNC_LEVEL_0101_39:03:009.0.3Security fixes; Flevel not incremented (whoops)
Mar-20190.101.2102FUNC_LEVEL_0101_29:02:009.0.2Security fixes; Flevel not incremented (whoops)
Mar-20190.100.394FUNC_LEVEL_0100_38:02:017.1.2Security fixes
Jan-20190.101.1102FUNC_LEVEL_0101_19:01:009.0.1Fix to clamav.h header; Adds clamav-types.h
Dec-20180.101.0100FUNC_LEVEL_01019:00:009.0.0Non-backwards compatible API/ABI change: Added filename to scanfile & scandesc, and scan options became a struct; RAR5 Support; Byte-Compare Subsigs; Add CL_TYPE_LNK
Sep-20180.100.293FUNC_LEVEL_0100_28:01:017.1.1Security fixes; Some lenience changes to FreshClam
Jun-20180.100.192FUNC_LEVEL_0100_18:01:017.1.1Security fixes; Add support for HTTPS in ClamSubmit
Mar-20180.99.485FUNC_LEVEL_099_48:01:017.1.1Security fixes; Other important bug fixes
Mar-20180.100.090FUNC_LEVEL_01008:01:017.1.1Feature release 2 years in dev't; Many improvements; Notably Container/Intermediates changes; Changes to wildcard signatures; PE Imp-hash signatures
Jan-20180.99.384FUNC_LEVEL_099_38:01:017.1.1Security fixes; Minor bug fixes
May-20160.99.282FUNC_LEVEL_099_28:01:017.1.1Various bug fixes
Mar-20160.99.182FUNC_LEVEL_099_18:01:017.1.1Security fixes; HWP support
Jan-20160.98.679FUNC_LEVEL_098_67:25:016.1.25Security fixes; Other bug fixes
Dec-20150.99.081FUNC_LEVEL_0998:01:017.1.1Add Yara and PCRE support; Add 'other' targets type (14) for non-listed target types; Improved on-access scanning.
May-20150.98.780FUNC_LEVEL_098_77:26:016.1.26Security fixes; MSXML & PDF fixes
Nov-20140.98.579FUNC_LEVEL_098_57:22:016.1.22Added internal target type (13); File properties JSON output.
Jun-20140.98.477FUNC_LEVEL_098_47:23:016.1.23
May-20140.98.377FUNC_LEVEL_098_37:22:016.1.22
May-20140.98.277FUNC_LEVEL_098_27:22:016.1.22Add engine_options bit field (and DisableCache option); Add stats callbacks and callback context
Jan-20140.98.176FUNC_LEVEL_098_17:20:016.1.20Added XZ support and ForceToDisk scan option; Added Libxml2 dependency + XAR, DMG, HFS+/HFSX support; Added FTM type 4 (for in-buffer partition magic, analogous to type 0 for files)
Sep-20130.98.074FUNC_LEVEL_0987:18:016.1.18Add Target-Types 10 - 13 (PDF, FLASH, JAVA, and INTERNAL); Introduced: all-scan, SWF & Java targets (11 & 12), "SE" offset modifier, ISO9660 support, wild card {}-bracket notation for body-based signatures; Disabled SWF parser
May-20130.97.869FUNC_LEVEL_097_87:17:016.1.17Security fixes
Mar-20130.97.768FUNC_LEVEL_097_77:16:016.1.16Security fixes
Sep-20120.97.667FUNC_LEVEL_097_67:15:016.1.15Fixed error-handling issues
Jun-20120.97.565FUNC_LEVEL_097_57:14:016.1.14First Sourcefire ClamAV release
Mar-20120.97.464FUNC_LEVEL_097_47:13:016.1.13Support comment lines in ALL DB files
Oct-20110.97.363FUNC_LEVEL_097_37:12:016.1.12
Jul-20110.97.262FUNC_LEVEL_097_27:11:016.1.11
Jun-20110.97.161FUNC_LEVEL_097_17:10:016.1.10
Feb-20110.97.060FUNC_LEVEL_0977:09:016.1.9
Nov-20100.96.558FUNC_LEVEL_096_57:07:016.1.7
Oct-20100.96.456FUNC_LEVEL_096_47:06:016.1.6Minimal FLEVEL allowed for all current bytecode signatures (quadratic load-time before this point)
Sep-20100.96.355FUNC_LEVEL_096_37:05:016.1.5
Aug-20100.96.254FUNC_LEVEL_096_27:04:016.1.4
May-20100.96.153FUNC_LEVEL_096_17:03:016.1.3
Mar-20100.9651FUNC_LEVEL_0967:02:016.1.2Add bytecode & CDB signatures, Ignores should use IGN2 (or take name field only from IGN)
Oct-20090.95.3446:05:006.0.5
Jun-20090.95.2436:04:006.0.4
May-20090.95.1426:03:006.0.3
Mar-20090.95416:02:006.0.2Ignores should use IGN format (including line number)

For more information on ClamAV file type support, see the File Types Reference.