VulnerabilityPublished 24 Sep 2026

CVE-2026-61816: zbateson mail-mime-parser · Uncontrolled Resource Consumption

Affects zbateson mail-mime-parserSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High : upgrade to 4.0.2 or 3.0.6 soon.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.0.2, 3.0.6

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 24 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 7 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 mail-mime-parser and zbateson/mail-mime-parser to 4.0.2 or 3.0.6.

Affected software

Product	Affected	Fixed in
zbatesonmail-mime-parser	Affected >=4.0.0 <4.0.2	Fixed in 4.0.2
zbatesonmail-mime-parser	Affected >=2.0.0 <3.0.6	Fixed in 3.0.6
Packagistzbateson/mail-mime-parser`pkg:composer/zbateson/mail-mime-parser`Other threats	Affected >=2.0.0 <3.0.6 >=4.0.0 <4.0.2	Fixed in 3.0.6 4.0.2

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 zbateson mail-mime-parser versions 3.0.6 and 4.0.2 and later. Users should upgrade to one of these fixed versions to fully mitigate the vulnerability. For users on end-of-life 2.x versions, upgrading to a fixed release is strongly advised as no patches will be provided. Until upgrading, restrict the parser's exposure to untrusted input and run parsing operations under constrained memory_limit and execution time limits to prevent resource exhaustion from malicious messages.

Description

zbateson/mail-mime-parser is a mail mime parser alternative to PHP's imap* functions and Pear libraries for reading messages in Internet Message Format RFC 822. Starting in version 2.0.0 and prior to version 3.0.6 and 4.0.2, an uncontrolled resource consumption / algorithmic complexity vulnerability (CWE-400) affects any application that parses untrusted email with this library. Three independent parsing paths are super-linear in cost, so a byte-size cap on the caller side does **not** bound the work done. A crafted message under 2 MB can consume seconds of CPU or hundreds of megabytes to multiple gigabytes of memory (leading to an out-of-memory kill), enabling denial of service. The parse is lazy, but the cost is paid on the first `getAllParts()` or content read. This is fxed in 4.0.2 and 3.0.6. The fixes add configurable limits on multipart nesting depth and on header count / total header size (recording a parse error past the threshold rather than throwing), and change sibling append to O(n). Users should upgrade to one of these (or later) versions. Versions 2.x are also affected but are end-of-life and will not receive patches; users on those lines should upgrade to a fixed release. (Versions prior to 2.0 used a different parser and are not affected by all three paths.) These costs are super-linear, so an input byte-size cap alone does not bound them. Until upgrading, restrict exposure of the parser to untrusted input, and run parsing under a constrained memory_limit and execution time limit so a malicious message fails its own request rather than exhausting the host.

Impact

Exploitation of this vulnerability can cause denial of service by exhausting CPU and memory resources on the host system running the mail-mime-parser library. Crafted email messages under 2 MB can trigger super-linear resource consumption, leading to prolonged processing times and potential out-of-memory conditions that may kill the process or degrade system availability. There is no impact on confidentiality or integrity reported. The vulnerability affects applications parsing untrusted email with the affected versions of the library.

Summary

The zbateson mail-mime-parser library, used for parsing email messages in Internet Message Format (RFC 822), contains an uncontrolled resource consumption vulnerability (CWE-400) in versions >=2.0.0 <3.0.6 and >=4.0.0 <4.0.2. Three independent parsing paths exhibit super-linear algorithmic complexity, causing CPU and memory usage to grow disproportionately relative to input size. This allows crafted messages under 2 MB to consume seconds of CPU time and hundreds of megabytes to multiple gigabytes of memory, potentially causing out-of-memory kills and denial of service. The vulnerability manifests when the parser's lazy evaluation triggers on the first call to getAllParts() or content read. Fixes in versions 3.0.6 and 4.0.2 introduce configurable limits on multipart nesting depth and header count/size, and optimize sibling append operations to linear time. Versions 2.x are affected but no longer maintained; upgrading to fixed versions is strongly recommended. Until patched, users should limit exposure to untrusted input and enforce memory and execution time constraints to mitigate impact.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/zbateson/mail-mime-parser/security/advisories/GHSA-f6v3-2qmr-vfjx (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Oct 2026, 18:56 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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