Highly exploitable, CVE-2026-61816 poses a critical security risk that could lead to severe breaches.
Status: Received on 24 Sep 2026, 18:17 UTC
Published on: 24 Sep 2026, 18:17 UTC
CVSS Release: version 3
security-advisories@github.com
Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVE-2026-61816: 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.
The exploitability of CVE-2026-61816 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
With low attack complexity and no required privileges, CVE-2026-61816 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-61816, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-61816, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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