5.9 CVE-2026-54411
Linux-PAM through 1.7.2 contains an observable timing discrepancy (CWE-208) in the pam_userdb module's plaintext-password comparison path in modules/pam_userdb/pam_userdb.c that allows a local or network-adjacent attacker able to repeatedly drive authentication through a calling service to recover the plaintext password of a target account by measuring response-timing differences. The comparison uses strncmp() (or strncasecmp() when PAM_ICASE_ARG is set) preceded by a length-equality check, so the time to reject a candidate depends on the index of the first differing byte and on whether the candidate's length matches the stored password, leaking the password length and individual prefix bytes. The vulnerable path is reached when the administrator configures pam_userdb with crypt=none, with an unrecognized crypt method, or without a crypt= argument, causing the module to store and compare credentials in plaintext.
https://nvd.nist.gov/vuln/detail/CVE-2026-54411
Categories
CWE-208 : Observable Timing Discrepancy
In security-relevant contexts, even small variations in timing can be exploited by attackers to indirectly infer certain details about the product's internal operations. For example, in some cryptographic algorithms, attackers can use timing differences to infer certain properties about a private key, making the key easier to guess. Timing discrepancies effectively form a timing side channel.
References
309f9ea4-e3e9-4c6c-b79d-e8eb01244f2c
AFFECTED (from MITRE)
| Vendor |
Product |
Versions |
| Linux-PAM |
Linux-PAM |
|
| © 2022 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. |
CPE
REMEDIATION
EXPLOITS
Exploit-db.com
| id |
description |
date |
|
| No known exploits |
POC Github
Other Nist (github, ...)
CAPEC
Common Attack Pattern Enumerations and Classifications
| id |
description |
severity |
| 462 |
Cross-Domain Search Timing
An attacker initiates cross domain HTTP / GET requests and times the server responses. The timing of these responses may leak important information on what is happening on the server. Browser's same origin policy prevents the attacker from directly reading the server responses (in the absence of any other weaknesses), but does not prevent the attacker from timing the responses to requests that the attacker issued cross domain. [Determine service to send cross domain requests to] The adversary first determines which service they will be sending the requests to [Send and time various cross domain requests] Adversaries will send a variety of cross domain requests to the target, timing the time it takes for the target to respond. Although they won't be able to read the response, the adversary can use the time to infer information about what the service did upon receiving the request. [Infer information from the response time] After obtaining reponse times to various requests, the adversary will compare these times and infer potentially sensitive information. An example of this could be asking a service to retrieve information and random usernames. If one request took longer to process, it is likely that a user with that username exists, which could be useful knowledge to an adversary. |
Medium |
| 541 |
Application Fingerprinting
An adversary engages in fingerprinting activities to determine the type or version of an application installed on a remote target. |
Low |
| 580 |
System Footprinting
An adversary engages in active probing and exploration activities to determine security information about a remote target system. Often times adversaries will rely on remote applications that can be probed for system configurations. |
Low |
MITRE
Techniques
| id |
description |
| T1082 |
System Information Discovery |
| T1592.002 |
Gather Victim Host Information: Software |
| © 2022 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. |
Mitigations
| id |
description |
| M1056 |
This technique cannot be easily mitigated with preventive controls since it is based on behaviors performed outside of the scope of enterprise defenses and controls. Efforts should focus on minimizing the amount and sensitivity of data available to external parties. |
| © 2022 The MITRE Corporation. Esta obra se reproduce y distribuye con el permiso de The MITRE Corporation. |
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