Mercurial Improper Certificate Validation vulnerability

published 2019-10-29 7 y ago modified 2026-07-06 4 mo ago also GHSA-7gf7-7wx4-mxmw , PYSEC-2026-665 , EUVD-2022-1665

cvss: 5.9; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.8%; EPSS 0.8% chance of exploitation in 30 days, percentile 57%
public exploits: 0; none known

Mercurial before 1.6.4 fails to verify the Common Name field of SSL certificates which allows remote attackers who acquire a certificate signed by a Certificate Authority to perform a man-in-the-middle attack.

Patch / fix

fixed in 2 distros 1 links 2

pypi mercurial 1.6.4
mercurial mercurial 1.6.4

mercurial Debian 14, Debian 13, Debian 12 1.6.4-1

debian advisories DEBIAN-CVE-2010-4237

github.com/dscho/hg@4ea63fb commit
github.com/dscho/hg@89baabf commit

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2010-4237 updated 2026-11-05 cvss 4.3

Mercurial: Doesn't verify subject Common Name

Red Hat Enterprise Linux 6 mercurial, mercurial-hgk, emacs-mercurial, emacs-mercurial-el
affected: no fix planned “Will not fix”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.82% chance of exploitation in the next 30 days, higher than 57% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:P/A:N
OSV	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
GitHub	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem	package	affected	fixed in
pypi	mercurial	<1.6.4	1.6.4

Affected products

mercurial mercurial

Classification

Weakness

CWE-295 Improper Certificate Validation

References

github.com /dscho/hg/commit/4ea63fb25ceeeaaa4cd1026f733b7ea7672c30b3
web
github.com /dscho/hg/commit/89baabf4fb7abf30ef6fdcf3d455a7893e5cc145
web
bz.mercurial-scm.org /show_bug.cgi?id=2407
web, vendor-advisory
security-tracker.debian.org /tracker/CVE-2010-4237
web, third-party-advisory
bugzilla.redhat.com /show_bug.cgi?id=CVE-2010-4237
web, issue-tracking, third-party-advisory
bugs.debian.org /cgi-bin/bugreport.cgi?bug=598841
web, issue-tracking, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2010-4237
advisory
repo.mercurial-scm.org /hg/rev/6ab4a7d3c179
web
repo.mercurial-scm.org /hg/rev/f2937d6492c5
web
pypi.org /project/mercurial
package
github.com /advisories/GHSA-7gf7-7wx4-mxmw
advisory

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary