VulnerabilityPublished 18 Sep 2026

CVE-2026-71537: paymenter/paymenter · Paymenter has a credit-refund double-spend race condition in service downgrade (doUpgrade)

Affects paymenter/paymenterSource GCVE Database

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 1.5.7 when convenient.

Data as of 2 Nov 2026, 22:58 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.5.7

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
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

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 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 paymenter/paymenter to 1.5.7.

Affected software

Product	Affected	Fixed in
Packagistpaymenter/paymenter	Affected <1.5.7	Fixed in 1.5.7

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

AI-suggested

A patch is available for this vulnerability. Operators should upgrade to Paymenter version 1.5.7 or later, where the issue is fixed by implementing proper transactional safety and database locking to serialize concurrent downgrade requests. Until patched, no reliable workaround is described. Users should apply the official fix to prevent exploitation.

Description

Paymenter payment platform versions prior to 1.5.7 contain a race condition in the service downgrade process that allows authenticated users to trigger multiple refunds for a single downgrade. This occurs because the downgrade logic lacks transactional safety and proper database locking, enabling concurrent requests to bypass concurrency checks and inflate user credit balances. The inflated credits can be used immediately for future payments or service provisioning, causing direct financial loss to the operator.

Impact

Authenticated users with active, downgradable services can exploit this race condition to inflate their credit balance by multiple times the legitimate refund amount. The inflated credits are real and spendable within the platform, allowing immediate use to pay invoices or acquire additional services. This leads to direct financial and resource losses for the Paymenter operator. There is no indication of data confidentiality or availability impact.

Summary

The vulnerability in Paymenter (CVE-2026-71537) arises from the doUpgrade() function in app/Livewire/Services/Upgrade.php, which processes service downgrades. The function performs a proration calculation and refunds user credits without wrapping these operations in a database transaction or applying row-level locks. The concurrency check relies on an unlocked read query to detect pending upgrades, which can be simultaneously passed by multiple concurrent requests. Each request inserts a pending upgrade record and increments the user's credit balance independently, resulting in multiple refunds for a single downgrade event. This race condition enables users to multiply their credit balance fraudulently.

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition) (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Sep 2026, 01:56 UTC

WeaknessesCWE-362

Technical details

References

Community reviews

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