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🛡️ CVE-2026-68750 — html-sanitize-ex

🟠 CVSS 7.5 — High ✅ No Known Exploit CWE-407 NVD
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Quadratic sibling re-flattening in the html_sanitize_ex traversal engine allows CPU-exhaustion denial of service

Summary

Inefficient Algorithmic Complexity vulnerability in the traversal engine in rrrene html\_sanitize\_ex allows an unauthenticated remote attacker to exhaust server CPU and memory via a flat run of sibling elements in sanitized HTML. The list clause of HtmlSanitizeEx.Traverser.traverse/2 recurses on the tail of a sibling list and then evaluates List.flatten(\[head\] ++ tail) over the already flattened result, so every one of n siblings copies and re-walks the entire remaining tail. The flattening is only needed for the rare case where scrub returns several replacement nodes for one node, but the cost is paid across the whole tail at every step, making traversal quadratic in sibling count.

The traverser sits on every public entry point, so no particular scrubber or configuration is required and the payload needs only allowed tags. A 160 KB body of 20,000 sibling elements occupies a scheduler for roughly 1.7 seconds, and the cost grows faster than the body does.

This issue affects html\_sanitize\_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.

Workaround

Cap the size of user-supplied HTML, and in particular the node count, before it reaches the sanitizer. The quadratic growth means the cap has to be small to be effective.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-68750 is classified as CWE-407: Inefficient Algorithmic Complexity. Crafted input drives an algorithm into its worst case, so a small request costs disproportionate work.

Affected software

CVE-2026-68750 is recorded against 2 packages.

  • html-sanitize-ex
  • htmlsanitizeex (from 0.3.1 up to 1.5.3)

Timeline and source

Published on 6 August 2026 and last revised on 19 August 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com (Advisory)
cna.erlef.org (Web)
github.com (Fix)
github.com (Fix)
hex.pm (Package)

Other advisories for this package

html-sanitize-ex has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-407: Inefficient Algorithmic Complexity) in other software:

Details

Severity High
CVSS Score 7.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-407
Public Exploit ✅ No
Source NVD
Published 2026-08-06
Updated 2026-08-20
Modified 2026-08-19

Affected Packages

Software From version Fixed in
html-sanitize-ex — —
htmlsanitizeex 0.3.1 1.5.3

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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