X.Org up to 1.19.0 XDM os/auth.c XdmToID information disclosure

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.0	$0-$5k	0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in X.Org up to 1.19.0. This issue affects the function XdmToID of the file os/auth.c of the component XDM. The manipulation leads to information disclosure. This vulnerability is listed as CVE-2017-2624. The attack must be carried out locally. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in X.Org up to 1.19.0. It has been rated as critical. This issue affects the function XdmToID of the file os/auth.c of the component XDM. The manipulation with an unknown input leads to a information disclosure vulnerability. Using CWE to declare the problem leads to CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

It was found that xorg-x11-server before 1.19.0 including uses memcmp() to check the received MIT cookie against a series of valid cookies. If the cookie is correct, it is allowed to attach to the Xorg session. Since most memcmp() implementations return after an invalid byte is seen, this causes a time difference between a valid and invalid byte, which could allow an efficient brute force attack.

The bug was discovered 02/28/2017. The weakness was presented 02/28/2017 by Eric Sesterhenn with X41 D-Sec GmbH as Advisory X41-2017-001: Multiple Vulnerabilities in X.org as confirmed mailinglist post (Full-Disclosure). It is possible to read the advisory at seclists.org. The identification of this vulnerability is CVE-2017-2624 since 12/01/2016. The exploitation is known to be easy. Attacking locally is a requirement. The successful exploitation needs a simple authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK. The following code is the reason for this vulnerability:

XdmToID(unsigned short cookie_length, char *cookie)
{
   XdmAuthorizationPtr auth;
   XdmClientAuthPtr client;
   unsigned char *plain;

   plain = malloc(cookie_length);
   if (!plain)
      return (XID) -1;
   for (auth = xdmAuth; auth; auth = auth->next) {
      XdmcpUnwrap((unsigned char *) cookie, (unsigned char *) &auth->key,
               plain, cookie_length);
      if ((client =
          XdmAuthorizationValidate(plain, cookie_length, &auth->rho, NULL,
                             NULL)) != NULL) {
         free(client);
         free(cookie);
         free(plain);
         return auth->id;
      }
   }
   free(cookie);
   free(plain);
   return (XID) -1;
}

The vulnerability scanner Nessus provides a plugin with the ID 101949 (Ubuntu 14.04 LTS / 16.04 LTS / 17.04 : xorg-server, xorg-server-hwe-16.04, xorg-server-lts-xenial vulnerabilities (USN-3362-1)), which helps to determine the existence of the flaw in a target environment. It is assigned to the family Ubuntu Local Security Checks and running in the context l. The commercial vulnerability scanner Qualys is able to test this issue with plugin 196856 (Ubuntu Security Notification for Xorg-server, Xorg-server-hwe-16.04, Xorg-server-lts-xenial Vulnerabilities (USN-3362-1)).

Upgrading eliminates this vulnerability. A possible mitigation has been published 6 months after the disclosure of the vulnerability.

The vulnerability is also documented in the databases at Tenable (101949), SecurityFocus (BID 96480†) and SecurityTracker (ID 1037919†). See VDB-97342, VDB-97344, VDB-97345 and VDB-97346 for similar entries. Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Name

• X.Org

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19.0

License

• open-source

CPE 2.3info

• 🔍
• 🔍
• 🔍

CPE 2.2info

• 🔍
• 🔍
• 🔍

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.1
VulDB Meta Temp Score: 6.0

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 7.0
NVD Vector: 🔍

CNA Base Score: 5.9
CNA Vector: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

NVD Base Score: 🔍

Exploitinginfo

Class: Information disclosure
CWE: CWE-200 / CWE-284 / CWE-266
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: No

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Nessus ID: 101949
Nessus Name: Ubuntu 14.04 LTS / 16.04 LTS / 17.04 : xorg-server, xorg-server-hwe-16.04, xorg-server-lts-xenial vulnerabilities (USN-3362-1)
Nessus File: 🔍
Nessus Risk: 🔍
Nessus Family: 🔍
Nessus Context: 🔍

OpenVAS ID: 841810
OpenVAS Name: Ubuntu Update for xorg-server USN-3362-1
OpenVAS File: 🔍
OpenVAS Family: 🔍

Qualys ID: 🔍
Qualys Name: 🔍

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

Reaction Time: 🔍
0-Day Time: 🔍
Exposure Time: 🔍

Timelineinfo

12/01/2016 🔍
02/28/2017 +89 days 🔍
02/28/2017 +0 days 🔍
02/28/2017 +0 days 🔍
02/28/2017 +0 days 🔍
02/28/2017 +0 days 🔍
07/24/2017 +146 days 🔍
07/25/2017 +1 days 🔍
07/27/2018 +367 days 🔍
08/29/2025 +2590 days 🔍

Sourcesinfo

Advisory: Advisory X41-2017-001: Multiple Vulnerabilities in X.org
Researcher: Eric Sesterhenn
Organization: X41 D-Sec GmbH
Status: Confirmed
Confirmation: 🔍

CVE: CVE-2017-2624 (🔍)
GCVE (CVE): GCVE-0-2017-2624
GCVE (VulDB): GCVE-100-97343
SecurityFocus: 96480 - X.org X Server Local Multiple Security Vulnerabilities
OSVDB: - CVE-2017-2624 - xorg-x11-server - Brute Force Issue
SecurityTracker: 1037919

See also: 🔍

Entryinfo

Created: 02/28/2017 20:24
Updated: 08/29/2025 16:56
Changes: 02/28/2017 20:24 (73), 08/18/2020 07:26 (17), 08/29/2025 16:56 (28)
Complete: 🔍
Cache ID: 216:A2D:103

Be aware that VulDB is the high quality source for vulnerability data.

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