CVE-2026-119283VulnerabilityPublished 31 Oct 2026

mcpm · joserfc: Unbounded JWE General JSON `recipients` Array Leads to CPU Exhaustion (DoS) via Repeated RSA Private-Key

Affects mcpmSource GCVE Database

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Authoritative record:CVE-2026-119283· High 7.5

Not known to be exploited · CVSS 7.5 High : upgrade to 2.15.0_3 soon.

Data as of 31 Oct 2026, 16:07 UTC

CVSS 3.1 base score

7.5High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.5

Patch: Available – fixed in 2.15.0_3

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

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

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: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 29 Oct 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 30 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 mcpm to 2.15.0_3.

Affected software

Product	Affected	Fixed in
Homebrewmcpm`pkg:brew/mcpm`Other threats	Affected >=2.14.0_4 <2.15.0_3	Fixed in 2.15.0_3

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 in joserfc version 2.15.0_3 that addresses this issue. Users should upgrade to this version or later to mitigate the CPU exhaustion vulnerability. The library's existing verify_all_recipients option does not mitigate CPU exhaustion and should not be relied upon. No other mitigations are documented.

Description

The joserfc library's decrypt_json() function for JWE General JSON Serialization does not limit the number of recipients in the 'recipients' array. An attacker can supply a JWE with an unbounded number of recipients, causing the library to perform a costly RSA private-key decryption operation for each recipient. This leads to a CPU exhaustion denial-of-service (DoS) condition. The library's documented mitigation option verify_all_recipients=False does not reduce CPU usage, as all recipients are decrypted unconditionally before this flag is checked. A fix is available in version 2.15.0_3.

Impact

An unauthenticated remote attacker can cause a denial-of-service condition by sending a JWE General JSON document with a large 'recipients' array to any endpoint using joserfc's decrypt_json() with an RSA private key. The victim server will perform an attacker-chosen number of expensive RSA private-key decryptions, exhausting CPU resources and potentially degrading or denying service. No confidentiality or integrity impact is described. The vulnerability affects availability only.

Summary

The joserfc library's public API decrypt_json() accepts a JWE General JSON Serialization input with an attacker-controlled 'recipients' array of unlimited length. For each recipient, the library performs a full RSA private-key decryption operation (decrypt_cek), with no upper bound on recipient count. This results in a linear increase in CPU consumption proportional to the number of recipients, enabling an unauthenticated network attacker to cause CPU exhaustion (DoS) with a single small HTTP request. The library caps sizes of other JWE elements but lacks any validation on the number of recipients. The decrypt loop calls decrypt_recipient() for every recipient before consulting the verify_all_recipients flag, rendering that mitigation ineffective against CPU exhaustion. This vulnerability corresponds to CWE-400 (Uncontrolled Resource Consumption) and has a CVSS v3.1 base score of 7.5 (High). The issue is fixed in joserfc version 2.15.0_3.

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Description

AI analysisMachine-generated, updated 31 Oct 2026, 16:07 UTC

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