CVE-2025-14759VulnerabilityPublished 17 Dec 2025

CVE-2025-14759: AWS S3 Encryption Client for .NET · Weak Cryptography

Affects AWS S3 Encryption Client for .NETSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.2.0 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 1% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.2.0

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

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

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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 17 Dec 2025
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 2026-10-25.

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 AWS S3 Encryption Client for .NET to 3.2.0.

Affected software

Product	Affected	Fixed in
AWS S3 Encryption Client for .NET	Affected <3.2.0	Fixed in 3.2.0

AI-suggested

European organizations should immediately upgrade the Amazon S3 Encryption Client for .NET to version 3.2.0 or later to ensure proper cryptographic key commitment is enforced. Additionally, organizations should audit their S3 bucket permissions to restrict write access strictly to trusted users and services, minimizing the risk of unauthorized key substitution. Implement monitoring and alerting on changes to S3 bucket contents, especially instruction files related to encryption metadata. Conduct regular integrity checks on encrypted data and validate encryption client versions in use across development and production environments. Incorporate cryptographic best practices by reviewing encryption key management policies and ensure that all cryptographic libraries are up to date. Finally, consider implementing additional layers of data integrity verification outside of the encryption client, such as application-level checksums or digital signatures, to detect tampering attempts.

Description

Missing cryptographic key commitment in the Amazon S3 Encryption Client for .NET may allow a user with write access to the S3 bucket to introduce a new EDK that decrypts to different plaintext when the encrypted data key is stored in an "instruction file" instead of S3's metadata record. To mitigate this issue, upgrade Amazon S3 Encryption Client for .NET to version 3.2.0 or later.

Impact

For European organizations, this vulnerability poses a significant risk to the integrity of encrypted data stored in S3 buckets when using the vulnerable .NET encryption client. Attackers with write access to the bucket could manipulate encrypted data keys, causing data to decrypt incorrectly or maliciously altered, potentially leading to corrupted data, application errors, or unauthorized data manipulation. This can undermine trust in data integrity, disrupt business processes relying on accurate data, and complicate forensic investigations. While confidentiality is not directly compromised, the integrity breach can have cascading effects on compliance with data protection regulations such as GDPR, especially if data tampering affects personal or sensitive information. Organizations relying heavily on AWS S3 for critical data storage and using the .NET encryption client are at higher risk. The medium CVSS score reflects moderate exploitability and significant integrity impact, emphasizing the need for timely remediation.

CWE-327Use of a Broken or Risky Cryptographic Algorithm (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a broken or risky cryptographic algorithm or protocol.
Architecture and Design · Libraries or Frameworks
When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations.
Architecture and Design
Ensure that the design allows one cryptographic algorithm to be replaced with another in the next generation or version. Where possible, use wrappers to make the interfaces uniform. This will make it easier to upgrade to stronger algorithms.
Architecture and Design
Carefully manage and protect cryptographic keys (see CWE-320). If the keys can be guessed or stolen, then the strength of the cryptography itself is irrelevant.
OWASP Cheat Sheets
Cryptographic Storage (opens in a new tab)
Key Management (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.7 (opens in a new tab)
V2.9.3 (opens in a new tab)
V6.2.2 (opens in a new tab)
Attack patterns
Encryption Brute Forcing (opens in a new tab)
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoof (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
Cryptanalysis of Cellular Encryption (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 24 Dec 2025, 20:43 UTC

WeaknessesCWE-327

Technical details

References

Community reviews

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