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CVE-2026-61816 high CVSS 7.5

Vulnerability in zbateson/mail-mime-parser (CVE-2026-61816)

Summary

Vulnerability in zbateson/mail-mime-parser (CVE-2026-61816). Risk of unauthorized operations or information disclosure. Exploitable via begin. Mitigation: upgrade to 4.0.2 or later.

Original description

The description as published by the source.

Impact

An uncontrolled resource consumption / algorithmic complexity vulnerability affecting 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.

Details

  1. Deep multipart nesting is O(depth²). MimeParserService::findContentBoundary() tests each content line against the current part and every ancestor via the recursive ParserMimePartProxy::setEndBoundaryFound(), so a nesting depth of D costs 1 + 2 + … + D comparisons. A ~600 KB message nested ~10,000 deep does not finish parsing in a minute.
  2. Many sibling parts is O(n²). PartChildrenContainer::add() appends each child with array_splice($children, count($children), 0, [$part]), which reindexes the entire array on every call. The same container backs UUEncoded begin parts via NonMimeParserService.
  3. Header buffering is unbounded. HeaderParserService::parse() reads header lines up to a blank line with no limit on header count or total size, so a few megabytes of header lines can hold hundreds of megabytes resident; a ~5 MB message of headers can reach multiple gigabytes and be OOM-killed.

##…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-61816 has been found in zbateson/mail-mime-parser.
Attackers can target a specific entry point like begin over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade zbateson/mail-mime-parser to 4.0.2 or later.
If unsure, ask your IT team or search "zbateson/mail-mime-parser CVE-2026-61816" on the vendor's site.

CVE-2026-61816 (zbateson/mail-mime-parser) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: begin / NonMimeParserService
Patched: 4.0.2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-400) exists in zbateson/mail-mime-parser. Attackers reach the vulnerable code path via begin without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of zbateson/mail-mime-parser. Attack surface: begin / NonMimeParserService.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.0.2.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'zbateson/mail-mime-parser' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'zbateson/mail-mime-parser' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で zbateson/mail-mime-parser を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade zbateson/mail-mime-parser to 4.0.2

    ステージング環境で 4.0.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

composer zbateson/mail-mime-parser
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.0.2"}]}]

References

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