CVE-2024-27355VulnerabilityPublished 1 Mar 2024Updated 13 Aug 2024

CVE-2024-27355: phpseclib · n/a

Affects phpseclibSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 1.0.23 soon.

Data as of 26 Oct 2026, 08:30 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 46% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.0.23

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

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

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: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; 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 impacted component (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).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 1 Mar 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 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 phpseclib/phpseclib to 1.0.23.

Affected software

Product	Affected	Fixed in
Packagistphpseclib/phpseclib`pkg:composer/phpseclib/phpseclib`Other threats	Affected <1.0.23	Fixed in 1.0.23

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

AI-suggested

1. Immediately upgrade phpseclib to version 1.0.23, 2.0.47, 3.0.36, or later, where the vulnerability has been patched. 2. Implement input validation and filtering to detect and block malformed or suspicious ASN.1 data before processing. 3. Employ rate limiting and resource usage monitoring on services that handle certificate parsing to detect abnormal CPU spikes indicative of exploitation attempts. 4. Use web application firewalls (WAFs) with custom rules to identify and block malicious payloads targeting ASN.1 parsing. 5. Conduct regular security audits and code reviews of cryptographic libraries and their usage within applications. 6. Isolate cryptographic processing in sandboxed environments to limit the impact of potential DoS attacks. 7. Maintain up-to-date threat intelligence to respond quickly if exploit code becomes available. 8. Educate development and operations teams about the risks of processing untrusted certificate data and the importance of timely patching.

Description

An issue was discovered in phpseclib 1.x before 1.0.23, 2.x before 2.0.47, and 3.x before 3.0.36. When processing the ASN.1 object identifier of a certificate, a sub identifier may be provided that leads to a denial of service (CPU consumption for decodeOID).

Impact

The primary impact of CVE-2024-27355 is denial of service through resource exhaustion, specifically high CPU consumption during ASN.1 OID decoding. Organizations using vulnerable phpseclib versions in their web applications or services that process certificates may experience service outages or degraded performance when exposed to crafted malicious inputs. This can disrupt critical operations, especially in environments relying on automated certificate validation or cryptographic functions, such as secure communications, authentication, or data encryption workflows. The vulnerability does not compromise data confidentiality or integrity but can cause significant operational downtime and potential cascading failures in dependent systems. Attackers can exploit this remotely without authentication or user interaction, increasing the risk of widespread disruption. The absence of known exploits in the wild currently limits immediate impact, but the ease of exploitation and high severity score indicate a strong potential for future attacks. Organizations with high availability requirements, such as financial institutions, cloud service providers, and government agencies, are particularly at risk of operational impact.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (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 26 Feb 2026, 11:01 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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