VulnerabilityPublished 23 Jun 2026

CVE-2026-54892: plug · Inefficient Algorithmic Complexity

Affects plugSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High · fixed in 1.19.3 : patch plug soon.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score

8.7High

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

EPSS: 0.8% chance of exploitation in 30 days – higher than 59% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.19.3, 1.18.3, 1.17.2 +2

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
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: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
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 23 Jun 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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
elixir-plugplug	Affected >=1.19.0 <1.19.3	Fixed in 1.19.3
elixir-plugplug	Affected >=1.18.0 <1.18.3	Fixed in 1.18.3
elixir-plugplug	Affected >=1.17.0 <1.17.2	Fixed in 1.17.2
elixir-plugplug	Affected >=1.16.0 <1.16.4	Fixed in 1.16.4
elixir-plugplug	Affected >=1.15.0 <1.15.5	Fixed in 1.15.5
elixir-plugplug	Affected ≥ 712b875d3442c765d8d37e546ffd5ad9f8afcc55, < c317d08fdcf96e17931f7419275b2b8c4bf3e951	Fixed in–

CPE configurations (1)

cpe:2.3:a:elixir-plug:plug:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until patches are confirmed, consider limiting the maximum allowed nesting depth in request parameters or applying rate limiting to mitigate potential denial of service. Monitor vendor channels for official fixes.

Description

Inefficient algorithmic complexity in Plug's nested-parameter decoder allows an unauthenticated remote attacker to cause denial of service. Plug.Conn.Query.decode/4 (and Plug.Conn.Query.decode_each/2) parse query strings and application/x-www-form-urlencoded request bodies. When a key contains many bracketed segments such as a[a][a][a]=1, the decoder walks the brackets and, for each of the N levels, performs a map operation keyed on an ever-growing binary prefix of the key, hashing the full byte range at each step. The total decode cost is therefore quadratic in the number of nesting levels. With the default Plug.Parsers.URLENCODED body limit of 1,000,000 bytes, a single request can carry roughly 333,000 nesting levels and saturate a BEAM scheduler for minutes. A small number of concurrent requests can saturate all schedulers and render a Plug-based server unresponsive. No authentication or knowledge of application routes is required. This vulnerability is associated with program files lib/plug/conn/query.ex and program routines Plug.Conn.Query.decode/4, Plug.Conn.Query.decode_each/2, Plug.Conn.Query.split_keys/6, Plug.Conn.Query.insert_keys/3, and Plug.Conn.Query.finalize_pointer/2. This issue affects plug from 1.15.0 before 1.15.5, 1.16.4, 1.17.2, 1.18.3, and 1.19.3.

Impact

An unauthenticated attacker can cause a denial of service by sending specially crafted requests with deeply nested parameters, leading to high CPU usage and server unresponsiveness. This affects availability of services using vulnerable plug versions.

Summary

CVE-2026-54892 describes an inefficient algorithmic complexity vulnerability (CWE-407) in the Plug.Conn.Query.decode/4 and related functions of the elixir-plug library. The vulnerability arises when parsing query strings or application/x-www-form-urlencoded bodies containing keys with many bracketed segments (e.g., a[a][a][a]=1). The decoder performs a map operation for each nesting level, with the cost growing quadratically relative to the number of nesting levels. With the default body size limit, a single request can contain approximately 333,000 nesting levels, saturating a BEAM scheduler for minutes. Multiple concurrent requests can exhaust all schedulers, causing a denial of service. No authentication or route knowledge is required to exploit this. Affected versions include 1.15.0 before 1.15.5, 1.16.0 before 1.16.4, 1.17.0 before 1.17.2, 1.18.0 before 1.18.3, and 1.19.0 before 1.19.3.

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 23 Jun 2026, 13:09 UTC

WeaknessesCWE-407

Technical details

References

Community reviews

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