Wednesday, August 21, 2019

Today we have published the ClamAV 0.101.4 security patch release.


ClamAV 0.101.4 is a security patch release that addresses the following issues.
  •  An out of bounds write was possible within ClamAV's NSIS bzip2 library when attempting decompression in cases where the number of selectors exceeded the max limit set by the library (CVE-2019-12900). The issue has been resolved by respecting that limit.

    Thanks to Martin Simmons for reporting the issue here.
  •  The zip bomb vulnerability mitigated in 0.101.3 has been assigned the CVE identifier CVE-2019-12625. Unfortunately, a workaround for the zip-bomb mitigation was immediately identified. To remediate the zip-bomb scan time issue, a scan time limit has been introduced in 0.101.4. This limit now resolves ClamAV's vulnerability to CVE-2019-12625.

    The default scan time limit is 2 minutes (120000 milliseconds).

    To customize the time limit:
    - use the clamscan  --max-scantime option
    - use the clamd  MaxScanTime config option

    Libclamav users may customize the time limit using the cl_engine_set_num function. For example:

        cl_engine_set_num(engine, CL_ENGINE_MAX_SCANTIME, time_limit_milliseconds)

    Thanks to David Fifield for reviewing the zip-bomb mitigation in 0.101.3 and reporting the issue.
As usual, ClamAV may be downloaded from, and discussion should take place on the ClamAV-Users list.  Thanks!

Monday, August 5, 2019

We are pleased to introduce the ClamAV 0.101.3 security patch release and a beta for the upcoming 0.102 feature release.

Both of these can be found on ClamAV's downloads site, with 0.101.3 in the "latest stable release" section and 0.102.0-beta in the beta section.


ClamAV 0.101.3 is a patch release to address a vulnerability to non-recursive zip bombs.

A Denial-of-Service (DoS) vulnerability may occur when scanning a zip bomb as a result of excessively long scan times. The issue is resolved by detecting the overlapping local file headers which characterize the non-recursive zip bomb described by David Fifield.

Thank you to Hanno Böck for reporting the issue as it relates to ClamAV, here.

Also included in 0.101.3:
  • Update of bundled the libmspack library from 0.8alpha to 0.10alpha, to address a buffer overflow vulnerability in libmspack < 0.9.1α.


ClamAV 0.102.0 includes an assortment of improvements and a couple of significant changes.

Major changes

  • The On-Access Scanning feature has been migrated out of clamd and into a brand new utility named clamonacc. This utility is similar to clamdscan and clamav-milter in that it acts as a client to clamd. This separation from clamd means that clamd no longer needs to run with root privileges while scanning potentially malicious files. Instead, clamd may drop privileges to run under an account that does not have super-user. In addition to improving the security posture of running clamd with On-Access enabled, this update fixed a few outstanding defects:
    • On-Access scanning for created and moved files (Extra-Scanning) is fixed.
    • VirusEvent for On-Access scans is fixed.
    • With clamonacc, it is now possible to copy, move, or remove a file if the scan triggered an alert, just like with clamdscan. For details on how to use the new clamonacc On-Access scanner, please refer to the user manual on, and keep an eye out for a new blog post on the topic
  • The freshclam database update utility has undergone a significant update. This includes:
    • Added support for HTTPS.
    • Support for database mirrors hosted on ports other than 80.
    • Removal of the mirror management feature (mirrors.dat).
    • An all new libfreshclam library API.

Notable changes

  • Added support for extracting ESTsoft .egg archives. This feature is new code developed from scratch using ESTsoft's Egg-archive specification and without referencing the UnEgg library provided by ESTsoft. This was necessary because the UnEgg library's license includes restrictions limiting the commercial use of the UnEgg library.
  • The documentation has moved!
    • Users should navigate to to view the documentation online.
    • The documentation will continue to be provided in HTML format with each release for offline viewing in the docs/html directory.
    • The new home for the documentation markdown is in our ClamAV FAQ Github repository.

Other improvements

  • Improved Windows executable Authenticode handling, enabling both whitelisting and blacklisting of files based on code-signing certificates. Additional improvements to Windows executable (PE file) parsing. Work courtesy of Andrew Williams.
  • Added support for creating bytecode signatures for Mach-O and ELF executable unpacking. Work courtesy of Jonas Zaddach.
  • Re-formatted the entire ClamAV code-base using clang-format in conjunction with our new ClamAV code style specification. See the blog post for details.
  • Integrated ClamAV with Google's OSS-Fuzz automated fuzzing service with the help of Alex Gaynor. This work has already proven beneficial, enabling us to identify and fix subtle bugs in both legacy code and newly developed code.
  • The clamsubmit tool is now available on Windows.
  • The clamscan metadata feature (--gen-json) is now available on Windows.
  • Significantly reduced number of warnings generated when compiling ClamAV with "-Wall" and "-Wextra" compiler flags and made many subtle improvements to the consistency of variable types throughout the code.
  • Updated the majority of third-party dependencies for ClamAV on Windows. The source code for each has been removed from the clamav-devel repository. This means that these dependencies have to be compiled independently of ClamAV. The added build process complexity is offset by significantly reducing the difficulty of releasing ClamAV with newer versions of those dependencies.
  • During the 0.102 development period, we've also improved our Continuous Integration (CI) processes. Most recently, we added a CI pipeline definition to the ClamAV Git repository. This chains together our build and quality assurance test suites and enables automatic testing of all proposed changes to ClamAV, with customizable parameters to suit the testing needs of any given code change.

Bug fixes

  • Fix to prevent a possible crash when loading LDB type signature databases and PCRE is not available. Patch courtesy of Tomasz Kojm.
  • Fixes to the PDF parser that will improve PDF malware detection efficacy. Patch courtesy of Clement Lecigne.
  • Fix for regular expression phishing signatures (PDB R-type signatures).
  • Various other bug fixes.

New Requirements

  • Libcurl has become a hard-dependency. Libcurl enables HTTPS support for freshclam and clamsubmit as well as communication between clamonacc and clamd.
  • Libcurl version >= 7.45 is required when building ClamAV from source with the new On-Access Scanning application (clamonacc). Users on Linux operating systems that package older versions of libcurl (e.g. all versions of CentOS and Debian versions <= 8) have a number of options:
    • Wait for your package maintainer to provide a newer version of libcurl.
    • Install a newer version of libcurl from source.
    • Disable installation of clamonacc and On-Access Scanning capabilities with the ./configure flag --disable-clamonacc.

      Non-Linux users will need to take no actions as they are unaffected by this new requirement.


The ClamAV team thanks the following individuals for their code submissions:
  • Alex Gaynor
  • Andrew Williams
  • Carlo Landmeter
  • Chips
  • Clement Lecigne
  • Paul Arthur
  • Jonas Zaddach
  • Ørjan Malde
  • Rick Wang
  • Rosen Penev
  • Thomas Jarosch
  • Tomasz Kojm

Finally, we'd like to thank Joe McGrath for building our quality assurance test suite and for working diligently to ensure knowledge transfer up until his last day on the team. Working with you was a pleasure, Joe, and we wish you the best of luck in your next adventure!