VulnerabilityPublished 3 Jun 2020Updated 9 Jun 2025

CVE-2020-11080: nghttp2 · Improper Enforcement of Message or Data Structure

Affects nghttp2Source CVE Database V5

Not known to be exploited · CVSS 3.7 Low : upgrade to 1.41.0 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

3.7Low

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

EPSS: 5.3% chance of exploitation in 30 days – higher than 92% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.41.0

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Jun 2020
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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 nghttp2/nghttp2 to 1.41.0.

Affected software

Product	Affected	Fixed in
GitHubnghttp2/nghttp2`pkg:github/nghttp2/nghttp2`Other threats	Affected <1.41.0	Fixed in 1.41.0

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

AI-suggested

European organizations should prioritize upgrading nghttp2 to version 1.41.0 or later to fully remediate this vulnerability. If immediate upgrade is not feasible, implement the recommended workaround by using the nghttp2_on_frame_recv_callback callback to monitor incoming SETTINGS frames and drop connections with an excessive number of settings entries (e.g., more than 32). Network-level protections such as rate limiting and anomaly detection on HTTP/2 traffic can help mitigate attack attempts by identifying and blocking abnormal SETTINGS frame sizes. Additionally, organizations should audit their software dependencies to identify all instances of nghttp2 usage, including embedded or third-party applications, to ensure comprehensive coverage. Regular monitoring of CPU usage and HTTP/2 traffic patterns can provide early detection of potential exploitation attempts. Finally, maintain up-to-date intrusion detection and prevention systems (IDS/IPS) with signatures or heuristics for abnormal HTTP/2 frames.

Description

In nghttp2 before version 1.41.0, the overly large HTTP/2 SETTINGS frame payload causes denial of service. The proof of concept attack involves a malicious client constructing a SETTINGS frame with a length of 14,400 bytes (2400 individual settings entries) over and over again. The attack causes the CPU to spike at 100%. nghttp2 v1.41.0 fixes this vulnerability. There is a workaround to this vulnerability. Implement nghttp2_on_frame_recv_callback callback, and if received frame is SETTINGS frame and the number of settings entries are large (e.g., > 32), then drop the connection.

Impact

For European organizations using nghttp2 versions prior to 1.41.0, this vulnerability poses a risk of denial of service through resource exhaustion. Systems acting as HTTP/2 servers or intermediaries that rely on nghttp2 could be targeted by attackers sending malicious SETTINGS frames, causing service degradation or outages. This can impact web services, APIs, or any applications using nghttp2 for HTTP/2 communication, potentially disrupting business operations and user access. While the vulnerability does not compromise data confidentiality or integrity, the availability impact can affect customer trust and operational continuity, especially for critical infrastructure or high-traffic web services. Organizations in sectors such as finance, telecommunications, and government, which often rely on robust HTTP/2 implementations, may experience service interruptions if unpatched. The lack of known exploits reduces immediate risk, but the simplicity of the attack vector (network access only) means opportunistic attackers could exploit unpatched systems.

CWE-707Improper Neutralization (opens in a new tab)
Pillar weakness
The product does not ensure or incorrectly ensures that structured messages or data are well-formed and that certain security properties are met before being read from an upstream component or sent to a downstream component.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
Attack patterns
XML Injection (opens in a new tab)
Inter-component Protocol Manipulation (opens in a new tab)
Data Interchange Protocol Manipulation (opens in a new tab)
Web Services Protocol Manipulation (opens in a new tab)
SOAP Manipulation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Jul 2025, 21:19 UTC

WeaknessesCWE-707

Technical details

References

Community reviews

Related threats