CVE-2024-39920VulnerabilityPublished 3 Jul 2024Updated 5 Aug 2024

CVE-2024-39920: n/a

Source CVE Database V5

Not known to be exploited · CVSS 4.3 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

4.3Medium

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Jul 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 2026-10-26.

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 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

AI-suggested

To mitigate the SnailLoad timing side-channel vulnerability, organizations should consider the following specific measures: 1) Limit or monitor slow-rate TCP connections from external or untrusted sources to reduce opportunities for attackers to establish the required slow concurrent connections. 2) Employ network segmentation and strict firewall rules to restrict access to client systems from potentially malicious servers, especially in sensitive environments. 3) Use encrypted and authenticated transport protocols (e.g., TLS) on top of TCP to reduce the value of inferred TCP-level information, as encrypted payloads limit the usefulness of timing side channels. 4) Monitor network traffic for unusual patterns of slow TCP connections or timing anomalies that could indicate exploitation attempts. 5) Stay informed about updates to TCP implementations and RFC 9293 revisions that may address this vulnerability, and apply patches promptly once available. 6) Consider deploying TCP implementations or operating system network stacks that incorporate side-channel resistant designs or mitigations. 7) For highly sensitive environments, consider additional application-layer protections such as traffic padding or obfuscation to reduce timing leakage. These measures go beyond generic advice by focusing on controlling attacker-controlled slow TCP connections and enhancing protocol-level confidentiality.

Description

The TCP protocol in RFC 9293 has a timing side channel that makes it easier for remote attackers to infer the content of one TCP connection from a client system (to any server), when that client system is concurrently obtaining TCP data at a slow rate from an attacker-controlled server, aka the "SnailLoad" issue. For example, the attack can begin by measuring RTTs via the TCP segments whose role is to provide an ACK control bit and an Acknowledgment Number.

Impact

The primary impact of CVE-2024-39920 is a reduction in confidentiality for TCP connections on affected client systems. Attackers can remotely infer information about the content or state of one TCP connection by exploiting timing side channels while the client communicates with an attacker-controlled server. This could lead to leakage of sensitive data transmitted over TCP, such as session tokens, credentials, or other private information, especially in multi-connection scenarios. Since the vulnerability does not affect integrity or availability, it does not enable data modification or denial of service. However, the ability to infer TCP connection content remotely without authentication poses a privacy risk and could facilitate further targeted attacks or reconnaissance. The medium CVSS score indicates a moderate risk level, but the actual impact depends on the sensitivity of the data transmitted and the network environment. Organizations with high-value or sensitive TCP traffic, such as financial institutions, healthcare providers, or government agencies, may face greater risk. The lack of known exploits in the wild suggests limited immediate threat, but the vulnerability could be leveraged in sophisticated attacks or combined with other vulnerabilities. The absence of patches means mitigation relies on network and system-level controls until protocol or implementation updates are available.

CWE-1255Comparison Logic is Vulnerable to Power Side-Channel Attacks (opens in a new tab)
Variant weakness
A device's real time power consumption may be monitored during security token evaluation and the information gleaned may be used to determine the value of the reference token.
Architecture and Design
The design phase must consider each check of a security token against a standard and the amount of power consumed during the check of a good token versus a bad token. The alternative is an all at once check where a retry counter is incremented PRIOR to the check.
Architecture and Design
Another potential mitigation is to parallelize shifting of secret data (see example 2 below). Note that the wider the bus the more effective the result.
Architecture and Design
An additional potential mitigation is to add random data to each crypto operation then subtract it out afterwards. This is highly effective but costly in performance, area, and power consumption. It also requires a random number generator.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Black Box Reverse Engineering (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 26 Feb 2026, 05:58 UTC

WeaknessesCWE-1255

Technical details

References

Community reviews

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