A mercurial security update has been released for Debian GNU/Linux 9 LTS to address several vulnerabilities.

DLA 2293-1: mercurial security update

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Debian LTS Advisory DLA-2293-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/
July 27, 2020   https://wiki.debian.org/LTS
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Package : mercurial
Version : 4.0-1+deb9u2
CVE ID : CVE-2017-17458 CVE-2018-13346 CVE-2018-13347 CVE-2018-13348
CVE-2018-1000132 CVE-2019-3902
Debian Bug : 901050 892964 927674

Several vulnerabilities were discovered in mercurial, an easy-to-use,
scalable distributed version control system.

CVE-2017-17458

In Mercurial before 4.4.1, it is possible that a specially
malformed repository can cause Git subrepositories to run
arbitrary code in the form of a .git/hooks/post-update script
checked into the repository. Typical use of Mercurial prevents
construction of such repositories, but they can be created
programmatically.

CVE-2018-13346

The mpatch_apply function in mpatch.c in Mercurial before 4.6.1
incorrectly proceeds in cases where the fragment start is past the
end of the original data.

CVE-2018-13347

mpatch.c in Mercurial before 4.6.1 mishandles integer addition and
subtraction.

CVE-2018-13348

The mpatch_decode function in mpatch.c in Mercurial before 4.6.1
mishandles certain situations where there should be at least 12
bytes remaining after the current position in the patch data, but
actually are not.

CVE-2018-1000132

Mercurial version 4.5 and earlier contains a Incorrect Access
Control (CWE-285) vulnerability in Protocol server that can result
in Unauthorized data access. This attack appear to be exploitable
via network connectivity. This vulnerability appears to have been
fixed in 4.5.1.

CVE-2019-3902

Symbolic links and subrepositories could be used defeat Mercurial's
path-checking logic and write files outside the repository root.

For Debian 9 stretch, these problems have been fixed in version
4.0-1+deb9u2.

We recommend that you upgrade your mercurial packages.

For the detailed security status of mercurial please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/mercurial

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://wiki.debian.org/LTS