S3 Encryption Client CVE-2025-14764

Exploitation requires three concrete conditions: (1) the victim must configure the S3 Encryption Client for Go to store the encrypted data key in an 'Instruction File' rather than in S3 object metadata - this is the specific non-default feature that disables effective key commitment; (2) the attacker must hold write/upload permission to the target S3 bucket (PR:L) to replace the existing instruction file; and (3) the attacker must be able to construct a rogue EDK that decrypts the existing ciphertext to a desired plaintext (the AT:P attack requirement, grounded in the Invisible Salamanders property of non-committing AEAD). Affected versions are <=v3.1. Limiting factors: default metadata-record storage is not vulnerable, the attacker needs pre-existing bucket write access, and impact is confined to integrity (returning forged plaintext) - no confidentiality or availability loss.

This is a genuine but narrowly-scoped cryptographic integrity flaw, not a high-urgency priority. The vendor CVSS 4.0 vector (6.0, Medium) scores integrity impact only (VI:H) with VC:N and VA:N - confidentiality and availability are untouched - so the 'Information Disclosure' tag is contradicted by the vector itself. Multiple mitigating signals align: EPSS is very low (0.11%, 1st percentile), there is no CISA KEV listing, and no public exploit code was identified. The attack requires both PR:L (write access to the target S3 bucket) and AT:P (a specific attack requirement - the attacker must be able to construct a rogue EDK that decrypts the same ciphertext to chosen plaintext, i.e. the 'Invisible Salamanders'/key-commitment property). It is further gated by a non-default deployment choice: the EDK must be stored in an 'Instruction File' rather than S3 object metadata. The signals are mutually consistent (low EPSS, no KEV, no POC, authenticated/write-gated, integrity-only) and point to a theoretical-to-targeted issue affecting a specific configuration rather than a broadly exploitable one. Confirmed facts: AWS security bulletin AWS-2025-032, GHSA-3g75-q268-r9r6, and fix in v4.0.0 all corroborate the affected-versions (<=3.1) and remediation.

An attacker who already holds write permission to a victim's S3 bucket that uses the S3 Encryption Client for Go in Instruction File mode crafts a rogue encrypted data key and uploads a replacement instruction file. The next time the legitimate application decrypts the underlying object, the client silently uses the attacker's rogue EDK and returns attacker-chosen plaintext instead of the original data. No public exploit code was identified, though the underlying 'Invisible Salamanders' technique is academically documented (eprint 2019/016).