VulnerabilityPublished 4 Apr 2024Updated 4 Nov 2025

CVE-2024-30255: envoyproxy envoy · Detection of Error Condition Without Action

Affects envoyproxy envoySource CVE Database V5

Not known to be exploited · 87% EPSS · CVSS 5.3 Medium : upgrade to 1.26.8 as a priority.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 87.8% chance of exploitation in 30 days – higher than 99% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.26.8

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

Attack Vector: Network
Attack Complexity: Low
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: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
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 4 Apr 2024
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 envoyproxy/envoy to 1.26.8.

Affected software

Product	Affected	Fixed in
GitHubenvoyproxy/envoy`pkg:github/envoyproxy/envoy`Other threats	Affected <1.26.8	Fixed in 1.26.8

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 immediately assess their Envoy deployments to identify versions affected by CVE-2024-30255. The primary mitigation is to upgrade Envoy to one of the patched versions: 1.29.3, 1.28.2, 1.27.4, or 1.26.8. This ensures the HTTP/2 codec properly limits CONTINUATION frames and prevents CPU exhaustion. If immediate upgrading is not feasible, organizations should consider disabling HTTP/2 protocol support on downstream connections to block the attack vector, understanding this may impact performance or compatibility. Network-level mitigations include deploying rate limiting or anomaly detection on HTTP/2 traffic to identify and block excessive CONTINUATION frames. Monitoring CPU usage patterns on Envoy instances can help detect ongoing exploitation attempts. Additionally, implementing Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with HTTP/2 protocol awareness can provide further protection. Organizations should also review their incident response plans to handle potential denial of service events related to this vulnerability. Regularly updating and patching Envoy and related infrastructure components remains critical to maintaining security posture.

Description

Envoy is a cloud-native, open source edge and service proxy. The HTTP/2 protocol stack in Envoy versions prior to 1.29.3, 1.28.2, 1.27.4, and 1.26.8 are vulnerable to CPU exhaustion due to flood of CONTINUATION frames. Envoy's HTTP/2 codec allows the client to send an unlimited number of CONTINUATION frames even after exceeding Envoy's header map limits. This allows an attacker to send a sequence of CONTINUATION frames without the END_HEADERS bit set causing CPU utilization, consuming approximately 1 core per 300Mbit/s of traffic and culminating in denial of service through CPU exhaustion. Users should upgrade to version 1.29.3, 1.28.2, 1.27.4, or 1.26.8 to mitigate the effects of the CONTINUATION flood. As a workaround, disable HTTP/2 protocol for downstream connections.

Impact

For European organizations, this vulnerability poses a risk of denial of service attacks targeting critical infrastructure that relies on Envoy proxies for edge routing, service mesh, or API gateway functions. High CPU utilization caused by malicious CONTINUATION frame floods can degrade service availability, leading to downtime or degraded performance of web applications, microservices, and cloud-native platforms. Organizations in sectors such as finance, telecommunications, government, and cloud service providers are particularly vulnerable due to their reliance on scalable and resilient proxy infrastructure. The attack requires no authentication, making public-facing Envoy instances attractive targets. Disruption could affect end-users and business operations, potentially causing financial loss and reputational damage. Additionally, the increased CPU load may lead to higher operational costs due to scaling or emergency incident response. While confidentiality and integrity are not directly impacted, the availability impact alone can be significant, especially for services with strict uptime requirements.

CWE-390Detection of Error Condition Without Action (opens in a new tab)
Base weaknessLikelihood of exploit: MediumOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product detects a specific error, but takes no actions to handle the error.
Implementation
Properly handle each exception. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.
Implementation
If a function returns an error, it is important to either fix the problem and try again, alert the user that an error has happened and let the program continue, or alert the user and close and cleanup the program.
Testing
Subject the product to extensive testing to discover some of the possible instances of where/how errors or return values are not handled. Consider testing techniques such as ad hoc, equivalence partitioning, robustness and fault tolerance, mutation, and fuzzing.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.8 (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

Description

AI analysisMachine-generated, updated 4 Nov 2025, 18:44 UTC

WeaknessesCWE-390

Technical details

References

Community reviews

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