Vulnerabilities > CVE-2020-10595 - Classic Buffer Overflow vulnerability in multiple products

047910
CVSS 7.5 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
PARTIAL
Integrity impact
PARTIAL
Availability impact
PARTIAL
network
low complexity
pam-krb5-project
debian
CWE-120
nessus
NVD
Published: 2020-03-31
Updated: 2020-04-04

Summary

pam-krb5 before 4.9 has a buffer overflow that might cause remote code execution in situations involving supplemental prompting by a Kerberos library. It may overflow a buffer provided by the underlying Kerberos library by a single '\0' byte if an attacker responds to a prompt with an answer of a carefully chosen length. The effect may range from heap corruption to stack corruption depending on the structure of the underlying Kerberos library, with unknown effects but possibly including code execution. This code path is not used for normal authentication, but only when the Kerberos library does supplemental prompting, such as with PKINIT or when using the non-standard no_prompt PAM configuration option.

Vulnerable Configurations

Part Description Count
Application
Pam-Krb5_Project
33
OS
Debian
3

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Buffer Overflow via Environment Variables
    This attack pattern involves causing a buffer overflow through manipulation of environment variables. Once the attacker finds that they can modify an environment variable, they may try to overflow associated buffers. This attack leverages implicit trust often placed in environment variables.
  • Overflow Buffers
    Buffer Overflow attacks target improper or missing bounds checking on buffer operations, typically triggered by input injected by an attacker. As a consequence, an attacker is able to write past the boundaries of allocated buffer regions in memory, causing a program crash or potentially redirection of execution as per the attackers' choice.
  • Client-side Injection-induced Buffer Overflow
    This type of attack exploits a buffer overflow vulnerability in targeted client software through injection of malicious content from a custom-built hostile service.
  • Filter Failure through Buffer Overflow
    In this attack, the idea is to cause an active filter to fail by causing an oversized transaction. An attacker may try to feed overly long input strings to the program in an attempt to overwhelm the filter (by causing a buffer overflow) and hoping that the filter does not fail securely (i.e. the user input is let into the system unfiltered).
  • MIME Conversion
    An attacker exploits a weakness in the MIME conversion routine to cause a buffer overflow and gain control over the mail server machine. The MIME system is designed to allow various different information formats to be interpreted and sent via e-mail. Attack points exist when data are converted to MIME compatible format and back.

Nessus

  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DSA-4648.NASL
    descriptionRuss Allbery discovered a buffer overflow in the PAM module for MIT Kerberos, which could result in denial of service or potentially the execution of arbitrary code.
    last seen2020-04-07
    modified2020-04-02
    plugin id135103
    published2020-04-02
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/135103
    titleDebian DSA-4648-1 : libpam-krb5 - security update
    code
    #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from Debian Security Advisory DSA-4648. The text 
# itself is copyright (C) Software in the Public Interest, Inc.
#

include("compat.inc");

if (description)
{
  script_id(135103);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/04/06");

  script_cve_id("CVE-2020-10595");
  script_xref(name:"DSA", value:"4648");

  script_name(english:"Debian DSA-4648-1 : libpam-krb5 - security update");
  script_summary(english:"Checks dpkg output for the updated package");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Debian host is missing a security-related update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"Russ Allbery discovered a buffer overflow in the PAM module for MIT
Kerberos, which could result in denial of service or potentially the
execution of arbitrary code."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://security-tracker.debian.org/tracker/source-package/libpam-krb5"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://packages.debian.org/source/stretch/libpam-krb5"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://packages.debian.org/source/buster/libpam-krb5"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://www.debian.org/security/2020/dsa-4648"
  );
  script_set_attribute(
    attribute:"solution", 
    value:
"Upgrade the libpam-krb5 packages.

For the oldstable distribution (stretch), this problem has been fixed
in version 4.7-4+deb9u1.

For the stable distribution (buster), this problem has been fixed in
version 4.8-2+deb10u1."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libpam-krb5");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:10.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:9.0");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/03/31");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/03/31");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/04/02");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"Debian Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Debian/release", "Host/Debian/dpkg-l");

  exit(0);
}


include("audit.inc");
include("debian_package.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Debian/release")) audit(AUDIT_OS_NOT, "Debian");
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;
if (deb_check(release:"10.0", prefix:"libpam-heimdal", reference:"4.8-2+deb10u1")) flag++;
if (deb_check(release:"10.0", prefix:"libpam-krb5", reference:"4.8-2+deb10u1")) flag++;
if (deb_check(release:"9.0", prefix:"libpam-heimdal", reference:"4.7-4+deb9u1")) flag++;
if (deb_check(release:"9.0", prefix:"libpam-krb5", reference:"4.7-4+deb9u1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:deb_report_get());
  else security_hole(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");
  • NASL familyDebian Local Security Checks
    NASL idDEBIAN_DLA-2166.NASL
    descriptionThe krb5 PAM module (pam_krb5.so) had a buffer overflow that might have caused remote code execution in situations involving supplemental prompting by a Kerberos library. It might have overflown a buffer provided by the underlying Kerberos library by a single
    last seen2020-04-07
    modified2020-04-02
    plugin id135101
    published2020-04-02
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/135101
    titleDebian DLA-2166-1 : libpam-krb5 security update
    code
    #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Debian Security Advisory DLA-2166-1. The text
# itself is copyright (C) Software in the Public Interest, Inc.
#

include("compat.inc");

if (description)
{
  script_id(135101);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/04/06");

  script_cve_id("CVE-2020-10595");

  script_name(english:"Debian DLA-2166-1 : libpam-krb5 security update");
  script_summary(english:"Checks dpkg output for the updated packages.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Debian host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"The krb5 PAM module (pam_krb5.so) had a buffer overflow that might
have caused remote code execution in situations involving supplemental
prompting by a Kerberos library. It might have overflown a buffer
provided by the underlying Kerberos library by a single '\0' byte if
an attacker responded to a prompt with an answer of a carefully chosen
length. The effect may have ranged from heap corruption to stack
corruption depending on the structure of the underlying Kerberos
library, with unknown effects but possibly including code execution.
This code path had not been used for normal authentication, but only
when the Kerberos library did supplemental prompting, such as with
PKINIT or when using the non-standard no_prompt PAM configuration
option.

For Debian 8 'Jessie', this problem has been fixed in version
4.6-3+deb8u1. The fix was prepared by Mike Gabriel.

We recommend that you upgrade your libpam-krb5 packages.

NOTE: Tenable Network Security has extracted the preceding description
block directly from the DLA security advisory. Tenable has attempted
to automatically clean and format it as much as possible without
introducing additional issues."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://lists.debian.org/debian-lts-announce/2020/04/msg00000.html"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://packages.debian.org/source/jessie/libpam-krb5"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Upgrade the affected libpam-heimdal, and libpam-krb5 packages."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libpam-heimdal");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libpam-krb5");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:8.0");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/03/31");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/04/01");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/04/02");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"Debian Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Debian/release", "Host/Debian/dpkg-l");

  exit(0);
}


include("audit.inc");
include("debian_package.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Debian/release")) audit(AUDIT_OS_NOT, "Debian");
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;
if (deb_check(release:"8.0", prefix:"libpam-heimdal", reference:"4.6-3+deb8u1")) flag++;
if (deb_check(release:"8.0", prefix:"libpam-krb5", reference:"4.6-3+deb8u1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:deb_report_get());
  else security_hole(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");
  • NASL familyUbuntu Local Security Checks
    NASL idUBUNTU_USN-4314-1.NASL
    descriptionRuss Allbery discovered that pam-krb5 incorrectly handled some responses. An attacker could possibly use this issue to execute arbitrary code. Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-04-07
    modified2020-04-02
    plugin id135170
    published2020-04-02
    reporterUbuntu Security Notice (C) 2020 Canonical, Inc. / NASL script (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/135170
    titleUbuntu 16.04 LTS / 18.04 LTS / 19.10 : libpam-krb5 vulnerability (USN-4314-1)
    code
    #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4314-1. The text 
# itself is copyright (C) Canonical, Inc. See 
# <http://www.ubuntu.com/usn/>. Ubuntu(R) is a registered 
# trademark of Canonical, Inc.
#

include("compat.inc");

if (description)
{
  script_id(135170);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/04/06");

  script_cve_id("CVE-2020-10595");
  script_xref(name:"USN", value:"4314-1");

  script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS / 19.10 : libpam-krb5 vulnerability (USN-4314-1)");
  script_summary(english:"Checks dpkg output for updated package.");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Ubuntu host is missing a security-related patch."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"Russ Allbery discovered that pam-krb5 incorrectly handled some
responses. An attacker could possibly use this issue to execute
arbitrary code.

Note that Tenable Network Security has extracted the preceding
description block directly from the Ubuntu security advisory. Tenable
has attempted to automatically clean and format it as much as possible
without introducing additional issues."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://usn.ubuntu.com/4314-1/"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Update the affected libpam-krb5 package."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libpam-krb5");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:14.04");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:19.10");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/03/31");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/03/31");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/04/02");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"Ubuntu Security Notice (C) 2020 Canonical, Inc. / NASL script (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"Ubuntu Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}


include("audit.inc");
include("ubuntu.inc");
include("misc_func.inc");

if ( ! get_kb_item("Host/local_checks_enabled") ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item("Host/Ubuntu/release");
if ( isnull(release) ) audit(AUDIT_OS_NOT, "Ubuntu");
release = chomp(release);
if (! preg(pattern:"^(12\.04|14\.04|16\.04|18\.04|19\.10)$", string:release)) audit(AUDIT_OS_NOT, "Ubuntu 12.04 / 14.04 / 16.04 / 18.04 / 19.10", "Ubuntu " + release);
if ( ! get_kb_item("Host/Debian/dpkg-l") ) audit(AUDIT_PACKAGE_LIST_MISSING);

cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Ubuntu", cpu);

flag = 0;

if (ubuntu_check(osver:"16.04", pkgname:"libpam-krb5", pkgver:"4.7-2ubuntu0.1")) flag++;
if (ubuntu_check(osver:"18.04", pkgname:"libpam-krb5", pkgver:"4.8-1ubuntu0.1")) flag++;
if (ubuntu_check(osver:"19.10", pkgname:"libpam-krb5", pkgver:"4.8-2ubuntu0.1")) flag++;

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : ubuntu_report_get()
  );
  exit(0);
}
else
{
  tested = ubuntu_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "libpam-krb5");
}

References