VulnerabilityPublished 24 Mar 2026

CVE-2026-33624: parse-server · Time-of-check Time-of-use (TOCTOU) Race Condition

Affects parse-serverSource CVE Database V5

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Not known to be exploited · CVSS 2.1 Low : upgrade to 9.6.0-alpha.54 or 8.6.60 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

2.1Low

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.6.0-alpha.54, 8.6.60

CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: High
Attack Requirements: Present
Privileges Required: High
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: High: The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques, for example, circumvention of address space randomization (ASLR) or data execution prevention (DEP) must be performed for the attack to be successful; Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: High: The attacker requires privileges that provide significant (e.g., administrative) control over the vulnerable system allowing full access to the vulnerable system’s settings and files.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Mar 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 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 parse-server to 9.6.0-alpha.54 or 8.6.60; parse-community/parse-server to 8.6.60.

Affected software

Product	Affected	Fixed in
parse-communityparse-server	Affected >=9.0.0 <9.6.0-alpha.54	Fixed in 9.6.0-alpha.54
parse-communityparse-server	Affected <8.6.60	Fixed in 8.6.60
GitHubparse-community/parse-server`pkg:github/parse-community/parse-server`Other threats	Affected <8.6.60	Fixed in 8.6.60

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

AI-suggested

Organizations should immediately upgrade parse-server to version 8.6.60 or later, or 9.6.0-alpha.54 or later, where the race condition has been fixed. In addition to patching, administrators should monitor authentication logs for unusual patterns of concurrent login attempts using MFA recovery codes, which may indicate exploitation attempts. Implementing rate limiting or throttling on login endpoints can reduce the feasibility of rapid concurrent requests needed to exploit this vulnerability. Educate users on safeguarding their passwords and MFA recovery codes to prevent credential theft. Consider deploying additional anomaly detection systems to flag suspicious authentication behaviors. For environments where immediate patching is not feasible, temporarily disabling MFA recovery codes or enforcing stricter session management policies may reduce risk. Finally, ensure that incident response plans include procedures for handling potential MFA recovery code abuse.

Description

CVE-2026-33624 is a TOCTOU race condition vulnerability in parse-community's parse-server affecting versions prior to 8.6.60 and 9.6.0-alpha.54. An attacker with a user's password and a single MFA recovery code can exploit concurrent login requests to reuse the recovery code multiple times, bypassing its intended single-use restriction. Exploitation requires high privileges (user password), a valid recovery code, and the ability to send rapid concurrent requests. This flaw undermines MFA recovery code security but does not allow unauthorized access without credentials. The vulnerability has a low CVSS score (2.

Impact

The primary impact of this vulnerability is the compromise of the intended single-use nature of MFA recovery codes. Attackers who have already obtained user credentials and a recovery code can reuse the recovery code multiple times to regain access to the account, potentially bypassing intended security controls. This could facilitate persistent unauthorized access, account takeover, or further lateral movement within an organization’s systems. While the vulnerability does not allow initial credential compromise, it weakens the security posture of MFA mechanisms, which are critical for protecting sensitive data and services. Organizations relying on parse-server for backend services, especially those managing sensitive user data or critical applications, may face increased risk of account abuse and reduced trust in MFA protections. The low CVSS score indicates limited impact scope and exploitation difficulty, but the risk is significant in environments where credential theft is possible or where attackers can perform high-speed concurrent requests.

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
Implementation
The most basic advice for TOCTOU vulnerabilities is to not perform a check before the use. This does not resolve the underlying issue of the execution of a function on a resource whose state and identity cannot be assured, but it does help to limit the false sense of security given by the check.
Implementation
When the file being altered is owned by the current user and group, set the effective gid and uid to that of the current user and group when executing this statement.
Architecture and Design
Limit the interleaving of operations on files from multiple processes.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.3 (opens in a new tab)
V11.1.6 (opens in a new tab)
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Race Conditions via Symbolic Links (opens in a new tab)
Leveraging Time-of-Check and Time-of-Use (TOCTOU) 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 31 Mar 2026, 20:18 UTC

WeaknessesCWE-367

Technical details

References

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