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LDAP Account Manager EUVDEUVD-2026-101595

| CVE-2026-55167 MEDIUM
Authentication Bypass by Capture-replay (CWE-294)
2026-10-14 security-advisories@github.com
4.2
CVSS 3.1 · Vendor: github
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Complete valid password authentication
  2. Exploit
    Retain WebAuthn challenge in same PHP session
  3. Execution
    Replay unconsumed signed ceremony state
  4. Impact
    Reuse 2FA instead of single-use enforcement

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Replay attack prevention
Exploitation Conditions

Exploitation requires LAM configured with WebAuthn two-factor authentication enabled (a non-default feature) on a version prior to 9.6. The attacker must have already completed valid password authentication, must operate within the same PHP session, and must present a valid authenticator signature - the signed WebAuthn ceremony state is not invalidated after the first response is processed, so it can be retained rather than consumed once. Limiting factors: a valid password and a genuine authenticator signature are both required, activity is confined to one existing PHP session, and the WebAuthn 2FA feature must be in use, collectively restricting impact to an already-partially-authenticated actor rather than an anonymous remote attacker.

Impact

This is a genuinely low-priority issue despite being a 2FA weakness. The CVSS base score of 4.2 (MEDIUM) is consistent with the vector CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N: although network-reachable (AV:N), it carries high attack complexity (AC:H) and requires prior low-level privilege (PR:L), meaning the attacker must already hold a valid password and operate within the same authenticated PHP session. No EPSS score was provided in the input, so exploitation probability cannot be quantified. The CVE is NOT on the CISA KEV list and no public exploit code was supplied, so exploitation status is 'no public exploit identified at time of analysis.' All signals align rather than conflict: low CVSS, no KEV, no POC, and a vendor-acknowledged narrow precondition chain (valid password + same session + valid authenticator signature). The CWE-294 (capture-replay) classification and the one-line fix (unset the WebAuthn session challenge) confirm this is a WebAuthn single-use enforcement gap, not a pre-authentication bypass. Net real-world risk is low and should be patched on a routine cycle rather than treated as an emergency.

Exploit ScenarioDerived

An attacker who already knows a victim's valid LAM password (or an authenticated insider) completes password authentication and, within the same PHP session, reuses the still-present signed WebAuthn ceremony state instead of it being consumed once, effectively reapplying the second factor rather than re-proving fresh possession of the authenticator. No public exploit code exists, and the high attack complexity plus the need for a captured valid authenticator signature and the same session make opportunistic exploitation impractical.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 14, 2026

WebAuthn two-factor authentication in LDAP Account Manager (LAM) before 9.6 fails to clear the WebAuthn challenge from the PHP session after the authentication response is processed, allowing a signed WebAuthn ceremony state to be replayed rather than consumed once. Exploitation requires an attacker who already holds valid account credentials (the CVSS vector shows PR:L, i.e. authenticated), operates within the same PHP session, and can present a valid authenticator signature, and it only affects non-default installations where WebAuthn 2FA is enabled - this is a low-priority 2FA weakness rather than an anonymous remote compromise. No public exploit code or confirmed active exploitation has been identified at time of analysis.

RemediationAI

Vendor-released patch: upgrade to LDAP Account Manager 9.6, which clears the WebAuthn challenge from the PHP session after the authentication response is processed (commit a56dcaab3e0f572283f5861404ed58d5ea301bc6; release notes at https://github.com/LDAPAccountManager/lam/releases/tag/9.6 and advisory at https://github.com/LDAPAccountManager/lam/security/advisories/GHSA-xgjg-fchx-x3g3). If an immediate upgrade is not possible, the affected code path can be avoided by disabling WebAuthn two-factor authentication for LAM accounts, at the cost of losing a second authentication factor until the upgrade is applied; alternatively, restrict administrative access to the LAM web interface to trusted networks or a reverse proxy with strong session controls, since the flaw is confined to a single already-partially-authenticated PHP session. Note that generic session hardening such as shorter session timeouts reduces but does not eliminate the replay window, because the stale challenge persists for the lifetime of the session itself. Because this is a low-severity, authenticated, non-default-feature issue, treat it as a routine patch-cycle item rather than an emergency.

Affected VersionsENISA

lam < 9.6

Affected Packages

euvd lam fix: 9.6

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

LAM is a PHP web frontend for administering LDAP directory entries such as users, groups and DHCP settings. Its WebAuthn implementation, in lib/webauthn.inc (class WebauthnManager), stores the WebAuthn authentication challenge in the PHP session ($_SESSION['webauthn_authentication']). Because that session key was not unset after a successful authentication response was validated, the signed ceremony state persisted and could be reused instead of being single-use. This maps to CWE-294 (Authentication Bypass by Capture-replay): the second factor's replay protection - the expectation that a challenge is consumed once - was effectively absent within a given session. The upstream fix is a one-line addition of unset($_SESSION['webauthn_authentication']) in the authentication path, shipped in release 9.6. The impact is bounded by the design of the flow: a valid password is still required to reach the WebAuthn step, the replay is confined to the same PHP session, and a genuine authenticator signature must still be produced, which is why the vector is high-complexity and low-severity.

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Severity by source

Vendor (github) PRIMARY 4.2 MEDIUM
AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N
vuln.today AI 3.1 LOW

Attacker must hold a valid password and a valid authenticator signature within the same session, so PR:L and AC:H; the replay weakens authentication integrity (I:L) without data disclosure (C:N) or availability loss (A:N).

3.1 AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
4.0 AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (github).

CVSS VectorVendor: github

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

Lifecycle Timeline

1
Patch available
Oct 14, 2026 - 20:34 EUVD

DescriptionCVE.org

LDAP Account Manager (LAM) is a webfrontend for managing entries (e.g. users, groups, DHCP settings) stored in an LDAP directory. Prior to 9.6, installations with WebAuthn two-factor authentication leave the challenge in the same PHP session after the authentication response is processed. A user who has already completed valid password authentication can therefore retain the same signed WebAuthn ceremony state instead of consuming it once. The practical risk is limited by the requirement for a valid password, the same PHP session, and a valid authenticator signature. This issue is fixed in version 9.6.

Threat Intelligence Overview

EPSS Score
0.2%
Top 90% exploitable
Prevalence
Low
niche open-source LDAP admin web frontend, limited enterprise footprint
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

21
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +21
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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