VulnerabilityPublished 6 Aug 2026Updated 19 Aug 2026

CVE-2026-68750: rrrene html_sanitize_ex · Inefficient Algorithmic Complexity

Affects rrrene html_sanitize_exSource CVE Database V5

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Not known to be exploited · CVSS 8.2 High : upgrade to 1.5.3 or 1.4.5 soon.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score

8.2High

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 56% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.5.3, 1.4.5

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: High
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; 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 Vulnerable System (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).
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 6 Aug 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 5 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 rrrene html_sanitize_ex to 1.5.3 or 1.4.5.

Affected software

Product	Affected	Fixed in
rrrenehtml_sanitize_ex	Affected >=1.5.0-rc.0 <1.5.3	Fixed in 1.5.3
rrrenehtml_sanitize_ex	Affected >=0.3.1 <1.4.5	Fixed in 1.4.5
rrrenehtml_sanitize_ex	Affected ≥ 69ea11d61525c470b39b6860d024770d5573ff1f, < 9f5ccedbed230930813f992a1e6906fcf485981e	Fixed in–
Hexhtml_sanitize_ex`pkg:hex/html_sanitize_ex`Other threats	Affected >=0.3.1 <1.4.5 >=1.5.0-rc.0 <1.5.3	Fixed in 1.4.5 1.5.3

CPE configurations (1)

cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*

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Description

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.

Impact

An unauthenticated remote attacker can exploit this vulnerability to cause denial of service by exhausting server CPU and memory resources. The inefficient traversal leads to excessive computation time and memory usage, potentially degrading or disrupting service availability.

Summary

The vulnerability arises from the traversal engine in rrrene's html_sanitize_ex library, specifically in the HtmlSanitizeEx.Traverser.traverse/2 function. This function recursively processes the tail of sibling elements and applies List.flatten on the concatenation of the head and tail, causing repeated copying and re-walking of the tail. This results in quadratic time complexity relative to the number of sibling elements. The traversal engine is invoked on every public entry point without requiring specific scrubber configurations, meaning an attacker only needs to supply allowed tags. For example, a payload with 20,000 sibling elements can occupy a scheduler for approximately 1.7 seconds, with resource consumption growing faster than the input size. The affected versions are from 0.3.1 before 1.5.3.

CWE-407Inefficient Algorithmic Complexity (opens in a new tab)
Class weaknessLikelihood of exploit: Low
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

CPE configurations (1)

Description

AI analysisMachine-generated, updated 13 Aug 2026, 17:15 UTC

WeaknessesCWE-407

Technical details

References

Community reviews

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