CVE-2026-59887Published

linkify-it: Quadratic-complexity DoS via the `mailto:` validator scan-loop on attacker text

Collected exploitation and prediction evidence

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-59887

Published

linkify-it is a links recognition library with full Unicode support. Prior to 5.0.2, the mailto: schema validator used by .test() and .match() can be invoked at every mailto: occurrence and scan the remaining input through src_email_name in lib/re.mjs, causing O(n^2) CPU consumption on crafted user text. This issue is fixed in version 5.0.2.

Source published: 8 Jul 2026 15:58:12 UTC
Source modified: 9 Jul 2026 14:41:02 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

euvd · EUVD-2026-42321

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Jul 8, 2026, 3:58:12 PM

dateUpdated: Jul 9, 2026, 2:41:02 PM

9 related source bulletins · separate from aliases

RHSA-2026:74609: Red Hat Security Advisory: Cluster Observability Operator 1.5.3

CVE-2026-19534 · CVE-2026-39244 · CVE-2026-41178 · CVE-2026-42504 · CVE-2026-45623 · CVE-2026-56864 · CVE-2026-56865 · CVE-2026-59887 · CVE-2026-63199 · CVE-2026-71556 · CVE-2026-73086 · CVE-2026-75899 · CVE-2026-75931 · CVE-2026-75975 · CVE-2026-76172 · CVE-2026-84292 · CVE-2026-84394 · CVE-2026-84445 · CVE-2026-84961 · CVE-2026-92000 · CVE-2026-100690

NCSC-2026-0325: Kwetsbaarheden verholpen in Atlassian producten

CVE-2021-44906 · CVE-2022-3517 · CVE-2023-45133 · CVE-2025-14813 · CVE-2026-0603 · CVE-2026-2332 · CVE-2026-3505 · CVE-2026-4800 · CVE-2026-6321 · CVE-2026-6322 · CVE-2026-10050 · CVE-2026-12143 · CVE-2026-12151 · CVE-2026-12802 · CVE-2026-12803 · CVE-2026-12816 · CVE-2026-13149 · CVE-2026-13506 · CVE-2026-13676 · CVE-2026-14257 · CVE-2026-14682 · CVE-2026-16221 · CVE-2026-18446 · CVE-2026-21582 · CVE-2026-24734 · CVE-2026-25639 · CVE-2026-27601 · CVE-2026-27606 · CVE-2026-29786 · CVE-2026-40983 · CVE-2026-40984 · CVE-2026-41284 · CVE-2026-41842 · CVE-2026-41845 · CVE-2026-41850 · CVE-2026-41851 · CVE-2026-41907 · CVE-2026-42033 · CVE-2026-42035 · CVE-2026-42041 · CVE-2026-42198 · CVE-2026-42583 · CVE-2026-42587 · CVE-2026-43513 · CVE-2026-44249 · CVE-2026-44486 · CVE-2026-44487 · CVE-2026-44488 · CVE-2026-44490 · CVE-2026-44492 · CVE-2026-44494 · CVE-2026-44495 · CVE-2026-44496 · CVE-2026-45416 · CVE-2026-45623 · CVE-2026-46625 · CVE-2026-47838 · CVE-2026-48043 · CVE-2026-48779 · CVE-2026-48801 · CVE-2026-50010 · CVE-2026-53434 · CVE-2026-54291 · CVE-2026-54512 · CVE-2026-54513 · CVE-2026-55685 · CVE-2026-55831 · CVE-2026-55833 · CVE-2026-56745 · CVE-2026-56819 · CVE-2026-58059 · CVE-2026-58060 · CVE-2026-59639 · CVE-2026-59642 · CVE-2026-59869 · CVE-2026-59871 · CVE-2026-59873 · CVE-2026-59874 · CVE-2026-59887 · CVE-2026-59901 · CVE-2026-67320 · CVE-2026-69152 · CVE-2026-69192

RHSA-2026:83662: Red Hat Security Advisory: MTV RHEL9 Images

CVE-2026-50162 · CVE-2026-56852 · CVE-2026-59887 · CVE-2026-84445 · CVE-2026-88031

RHSA-2026:83663: Red Hat Security Advisory: MTV RHEL9 Images

CVE-2026-50162 · CVE-2026-56852 · CVE-2026-59887 · CVE-2026-84445

RHSA-2026:89715: Red Hat Security Advisory: OpenShift Container Platform 4.16.74 bug fix and security update

CVE-2024-24786 · CVE-2026-14362 · CVE-2026-33814 · CVE-2026-39829 · CVE-2026-42151 · CVE-2026-46597 · CVE-2026-49329 · CVE-2026-59887 · CVE-2026-75888 · CVE-2026-83589 · CVE-2026-84292 · CVE-2026-93017 · CVE-2026-111943

WID-SEC-W-2026-2923: Atlassian Produkte (Bamboo, Bitbucket, Confluence, Crucible, Fisheye, und Jira): Mehrere Schwachstellen

CVE-2019-13990 · CVE-2021-44906 · CVE-2022-1471 · CVE-2022-23521 · CVE-2022-3517 · CVE-2022-41903 · CVE-2023-22518 · CVE-2023-22522 · CVE-2023-22523 · CVE-2023-22524 · CVE-2023-22527 · CVE-2023-45133 · CVE-2023-46604 · CVE-2025-14813 · CVE-2026-0603 · CVE-2026-10050 · CVE-2026-12143 · CVE-2026-12151 · CVE-2026-12802 · CVE-2026-12803 · CVE-2026-12816 · CVE-2026-13149 · CVE-2026-13506 · CVE-2026-13676 · CVE-2026-14257 · CVE-2026-14682 · CVE-2026-16221 · CVE-2026-18446 · CVE-2026-21582 · CVE-2026-2332 · CVE-2026-24734 · CVE-2026-25639 · CVE-2026-27601 · CVE-2026-27606 · CVE-2026-29786 · CVE-2026-3505 · CVE-2026-40983 · CVE-2026-40984 · CVE-2026-41284 · CVE-2026-41842 · CVE-2026-41845 · CVE-2026-41850 · CVE-2026-41851 · CVE-2026-41907 · CVE-2026-42033 · CVE-2026-42035 · CVE-2026-42041 · CVE-2026-42198 · CVE-2026-42583 · CVE-2026-42587 · CVE-2026-43513 · CVE-2026-44249 · CVE-2026-44486 · CVE-2026-44487 · CVE-2026-44488 · CVE-2026-44490 · CVE-2026-44492 · CVE-2026-44494 · CVE-2026-44495 · CVE-2026-44496 · CVE-2026-45416 · CVE-2026-45623 · CVE-2026-46625 · CVE-2026-47838 · CVE-2026-4800 · CVE-2026-48043 · CVE-2026-48779 · CVE-2026-48801 · CVE-2026-50010 · CVE-2026-53434 · CVE-2026-54291 · CVE-2026-54512 · CVE-2026-54513 · CVE-2026-55685 · CVE-2026-55831 · CVE-2026-55833 · CVE-2026-56745 · CVE-2026-56819 · CVE-2026-58059 · CVE-2026-58060 · CVE-2026-59639 · CVE-2026-59642 · CVE-2026-59869 · CVE-2026-59871 · CVE-2026-59873 · CVE-2026-59874 · CVE-2026-59887 · CVE-2026-59901 · CVE-2026-6321 · CVE-2026-6322 · CVE-2026-67320 · CVE-2026-69152 · CVE-2026-69192

RHSA-2026:89839: Red Hat Security Advisory: OpenShift Container Platform 4.14.77 bug fix and security update

CVE-2026-14362 · CVE-2026-33814 · CVE-2026-39821 · CVE-2026-55204 · CVE-2026-59887 · CVE-2026-111943

RHSA-2026:90321: Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.31.0 Release.

CVE-2023-54404 · CVE-2025-62718 · CVE-2026-8643 · CVE-2026-9496 · CVE-2026-12185 · CVE-2026-13697 · CVE-2026-14682 · CVE-2026-15076 · CVE-2026-16308 · CVE-2026-17106 · CVE-2026-18427 · CVE-2026-19203 · CVE-2026-19534 · CVE-2026-39820 · CVE-2026-41178 · CVE-2026-41707 · CVE-2026-42499 · CVE-2026-42502 · CVE-2026-45416 · CVE-2026-47884 · CVE-2026-47886 · CVE-2026-47888 · CVE-2026-47890 · CVE-2026-47892 · CVE-2026-50010 · CVE-2026-55831 · CVE-2026-55833 · CVE-2026-55851 · CVE-2026-56745 · CVE-2026-56746 · CVE-2026-56819 · CVE-2026-56852 · CVE-2026-56854 · CVE-2026-58062 · CVE-2026-59280 · CVE-2026-59282 · CVE-2026-59283 · CVE-2026-59296 · CVE-2026-59313 · CVE-2026-59323 · CVE-2026-59651 · CVE-2026-59887 · CVE-2026-59899 · CVE-2026-59901 · CVE-2026-62243 · CVE-2026-64607 · CVE-2026-67213 · CVE-2026-67312 · CVE-2026-67313 · CVE-2026-67314 · CVE-2026-67320 · CVE-2026-67321 · CVE-2026-68494 · CVE-2026-68497 · CVE-2026-69152 · CVE-2026-69192 · CVE-2026-71290 · CVE-2026-71324 · CVE-2026-71325 · CVE-2026-71327 · CVE-2026-73500 · CVE-2026-73508 · CVE-2026-74835 · CVE-2026-75838 · CVE-2026-75899 · CVE-2026-75931 · CVE-2026-76169 · CVE-2026-81521 · CVE-2026-82417 · CVE-2026-82562 · CVE-2026-84292 · CVE-2026-84375 · CVE-2026-84394 · CVE-2026-84428 · CVE-2026-84445 · CVE-2026-84469 · CVE-2026-84504 · CVE-2026-84961 · CVE-2026-85062 · CVE-2026-85124 · CVE-2026-85152 · CVE-2026-85595 · CVE-2026-85597 · CVE-2026-86063 · CVE-2026-87743 · CVE-2026-88004 · CVE-2026-88007 · CVE-2026-88008 · CVE-2026-88009 · CVE-2026-88011 · CVE-2026-88012 · CVE-2026-88031 · CVE-2026-88878 · CVE-2026-88879 · CVE-2026-90711 · CVE-2026-93749 · CVE-2026-100655 · CVE-2026-100656 · CVE-2026-100666 · CVE-2026-101916 · CVE-2026-102925 · CVE-2026-102930 · CVE-2026-103435 · CVE-2026-109618 · CVE-2026-109619

RHSA-2026:68754: Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.30.1 Release.

CVE-2026-4800 · CVE-2026-45623 · CVE-2026-45819 · CVE-2026-47219 · CVE-2026-48801 · CVE-2026-54272 · CVE-2026-55831 · CVE-2026-55833 · CVE-2026-56745 · CVE-2026-56746 · CVE-2026-56819 · CVE-2026-59887 · CVE-2026-59899 · CVE-2026-67213 · CVE-2026-67312 · CVE-2026-67313 · CVE-2026-67314 · CVE-2026-67320 · CVE-2026-67321 · CVE-2026-69152 · CVE-2026-69153 · CVE-2026-69192 · CVE-2026-71436 · CVE-2026-73086 · CVE-2026-73088 · CVE-2026-73089 · CVE-2026-73508 · CVE-2026-73566 · CVE-2026-73646 · CVE-2026-75899 · CVE-2026-75931 · CVE-2026-75975 · CVE-2026-76172 · CVE-2026-82562 · CVE-2026-84292 · CVE-2026-84375 · CVE-2026-84394

Source published: Jul 8, 2026, 3:58:12 PM (timezone not stated)
Source modified: Jul 9, 2026, 2:41:02 PM (timezone not stated)
Observed here: 7 Nov 2026 13:26:01 UTC
Source terms: ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd · CVE-2026-59887

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-407

Original publisher date fields

published: 2026-07-08T17:17:26.883

lastModified: 2026-10-25T17:10:00.197

1 source CPE criteria · context only

cpe:2.3:a:markdown-it:linkify-it:*:*:*:*:*:node.js:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 8 Jul 2026 17:17:26 UTC
Source modified: 25 Oct 2026 17:10:00 UTC
Observed here: 27 Oct 2026 15:15:33 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

osv · GHSA-v245-v573-v5vm

Published

### Summary `linkify-it`'s schema-scan loop (`.test()` / `.match()`, the documented public API) invokes the `mailto:` schema validator at **every** `mailto:` occurrence in the input text. For each occurrence the validator does `text.slice(pos)` (an O(n) copy) and runs an email regex whose local-part class `src_email_name` greedily scans the **entire remaining tail** (O(n)) before failing. With N `mailto:` occurrences that is **N × O(n) = O(n²)**. Because linkify-it runs on arbitrary user text (markdown-it feeds it whole documents when `linkify:true`), an unauthenticated attacker can block the single-threaded event loop for many seconds with a small input. No length bound (unlike an HTTP header). ### Root cause — `index.mjs` + `lib/re.mjs` ```js // index.mjs (mailto validator) — runs at every "mailto:" hit 'mailto:': { validate: function (text, pos, self) { const tail = text.slice(pos) // O(n) copy per hit if (!self.re.mailto) self.re.mailto = new RegExp('^' + self.re.src_email_name + '@' + self.re.src_host_strict, 'i') if (self.re.mailto.test(tail)) { ... } // scans the whole O(n) tail return 0 }} // lib/re.mjs:91-93 — every char of "mailto:" (incl. ':','-',';') is in this class: re.src_email_name = '[\\-;:&=\\+\\$,\\.a-zA-Z0-9_][\\-;:&=\\+\\$,\\"\\.a-zA-Z0-9_]*' ``` The `while ((m = re.exec(text)) !== null) { …testSchemaAt… }` scan loop calls the validator at each `mailto:` hit; `src_email_name` greedily consumes the whole tail (all chars are in its class) then fails for lack of `@`. `http:`/`https:` do NOT blow up — their validator requires the tail to start with `//`, failing in O(1) per hit. ### Proof of Concept (confirmed, linkify-it 5.0.1, Node v24) ```js const LinkifyIt = require('linkify-it'); const lf = new LinkifyIt(); lf.match('mailto:'.repeat(48000)); // ~336 KB of "mailto:mailto:…" -> seconds of blocked event loop ``` | input (same bytes) | 56 KB | 112 KB | 224 KB | 336 KB | |---|---:|---:|---:|---:| | **`mailto:` contiguous** | 97 ms | 357 ms | 1438 ms | 3272 ms | | `mailto:` space-separated | 2 ms | 3 ms | 5 ms | 8 ms | | `http://` contiguous | 12 ms | 17 ms | 33 ms | 49 ms | ×~4 per 2× input ⇒ O(n²); equal-byte controls stay flat ⇒ algorithmic, not a GC/allocation artifact. Real-world via markdown-it 14.x (`{linkify:true}`), `md.render('mailto:'.repeat(n))`: 219 KB ≈ ~5 s. <img width="737" height="161" alt="image" src="https://github.com/user-attachments/assets/b5d390f3-68d0-4861-9c47-ad8aff0203d5" /> ### Impact Reachable on arbitrary user text via the documented `.test()`/`.match()` API and through markdown-it's linkifier — comment systems, chat, forums, wikis, note apps that render user markdown with linkify enabled. A ~220 KB post hangs the event loop ~5 s; a few hundred KB → tens of seconds. Availability only. ### Suggested remediation Bound the email local-part per RFC 5321 (≤64) so per-hit work is O(1), and avoid the full-tail slice: ```js // lib/re.mjs — cap the greedy run: re.src_email_name = '[\\-;:&=\\+\\$,\\.a-zA-Z0-9_][\\-;:&=\\+\\$,\\"\\.a-zA-Z0-9_]{0,63}' // index.mjs — prefer a sticky regex anchored at `pos` over text.slice(pos). ``` ### Affected / disclosure All versions through 5.0.1 (latest); same code on `master`. cve-mcp/OSV report no known vulnerability for linkify-it. Distinct from markdown-it's own `*`-run ReDoS (CVE-2026-2327, different package/path) and the recent markdown-it DoS. Reported privately; happy to test a patch against the PoC.

Source published: 21 Jul 2026 19:06:09 UTC
Source modified: 10 Sep 2026 03:51:12 UTC
Observed here: 24 Oct 2026 13:17:17 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH