VulnerabilityPublished 26 Jun 2026

CVE-2026-55164: Lemur user-update path stores plaintext passwords

Affects lemurSource GCVE Database

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Authoritative record:CVE-2026-55164· Medium 4.9

Not known to be exploited · CVSS 4.9 Medium : upgrade to 1.9.2 when convenient.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

4.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.9.2

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

Disclosed: evidence found.
CVE published 18 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CISA SSVC: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

CVE ID reserved
by GitHub, Inc.
16 Jun 202615:13 UTC, 63 days before disclosure
CVE published
on cve.org
18 Aug 202618:53 UTC, t = 0
CISA SSVC assessment
proof of concept public
18 Aug 202619:15 UTC, 22 minutes after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA SSVC, the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade lemur to 1.9.2.

Affected software

Product	Affected	Fixed in
PyPIlemur	Affected <1.9.2	Fixed in 1.9.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Lemur version 1.9.2 that addresses this issue by properly hashing passwords on update. Users should upgrade to version 1.9.2 or later to remediate this vulnerability. No other mitigation is indicated or required according to the vendor advisory.

Description

Lemur manages TLS certificate creation. Prior to 1.9.2, lemur.users.service.update assigned a replacement password directly to users.password, while lemur/users/models.py registered User.hash_password only for the before_insert event. Because no before_update listener ran, administrator-initiated password changes through PUT /api/1/users/ were committed as plaintext. The affected user could no longer authenticate normally because bcrypt verification received an unhashed value. A database, backup, replica, query-log, or administrative read compromise exposed immediately usable credentials without offline cracking. The fix registers hashing for before_update and avoids rehashing values that already have a bcrypt prefix. This issue is fixed in version 1.9.2.

Impact

The vulnerability leads to plaintext storage of user passwords during administrator-initiated updates, exposing credentials to immediate compromise if the database or related data stores are accessed by unauthorized parties. This undermines user authentication security and could allow attackers to impersonate users without needing to crack hashed passwords.

Summary

In Lemur versions before 1.9.2, the user password update path did not hash replacement passwords because the hashing function was only registered for the before_insert event, not before_update. As a result, when an administrator changed a user's password via the PUT /api/1/users/ endpoint, the new password was stored in plaintext in the database. This plaintext storage means that any compromise of the database, backups, replicas, or query logs could expose immediately usable credentials without requiring offline cracking. The fix in version 1.9.2 registers the password hashing function for the before_update event and ensures passwords with an existing bcrypt prefix are not rehashed.

CWE-256Plaintext Storage of a Password (opens in a new tab)
Base weaknessLikelihood of exploit: HighOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product stores a password in plaintext within resources such as memory or files.
Architecture and Design
Avoid storing passwords in easily accessible locations.
Architecture and Design
Consider storing cryptographic hashes of passwords as an alternative to storing in plaintext.
A programmer might attempt to remedy the password management problem by obscuring the password with an encoding function, such as base 64 encoding, but this effort does not adequately protect the password because the encoding can be detected and decoded easily.
OWASP Cheat Sheets
Forgot Password (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V2.7.5 (opens in a new tab)
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

Timeline

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Aug 2026, 11:15 UTC

WeaknessesCWE-256

Technical details

References

Community reviews

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