CVE-2015-2808: RC4 in TLS/SSL leaks plaintext via Invariance Weakness

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 18 September 2026. Confidence: high.

medium priorityThe CVSS score is low (3.7) and exploitation requires a network vantage point plus specific key conditions, but the very high EPSS and broad product footprint keep it relevant for legacy environments.

What it is

The RC4 stream cipher, as used in TLS and SSL, fails to properly combine state data with key data during initialization, leaving the initial keystream bytes biased. A remote attacker who can sniff network traffic can recover plaintext from the first bytes of affected sessions. This is the 'Bar Mitzvah' issue, a protocol-level weakness in RC4 rather than a bug in a single product.

Impact

An attacker who captures traffic gains partial plaintext recovery of the initial bytes of RC4-protected streams, which can expose sensitive data such as session tokens or credentials. The confidentiality impact is limited (CVSS C:L) and no integrity or availability loss is described.

Attack surface

Reachable over the network by sniffing TLS/SSL traffic that negotiates RC4; the CVSS vector shows no privileges and no user interaction required. The attacker must be positioned to observe the encrypted stream and must catch sessions using keys affected by the Invariance Weakness.

Exploitation

Not listed in CISA KEV and no ransomware association is recorded, but EPSS is very high (0.73851, 99.45th percentile), indicating strong predicted exploitation likelihood. All references are third-party advisories and mailing lists; none are tagged as exploit code.

What to do

• Disable RC4 cipher suites in TLS/SSL configurations on all servers and clients, prioritizing TLS 1.2+ with AEAD ciphers.
• Apply vendor updates for the listed products (Oracle, Red Hat, Debian, SUSE, Canonical, IBM, Huawei, Fujitsu) that remove or deprioritize RC4.
• Audit and remediate legacy appliances and firmware (e.g., ILOM, SPARC M3000 firmware) that may still offer RC4-only cipher suites.
• Enforce cipher policy centrally and monitor for RC4 negotiation in TLS handshakes across the estate.

Detection

• Inspect TLS handshake logs and packet captures for negotiated cipher suites containing RC4 (e.g., TLS_RSA_WITH_RC4_128_SHA).
• Alert on any internal or external service still accepting RC4-based connections after the remediation window.
• Correlate network flow records with TLS metadata to identify hosts that continue to negotiate RC4.
• Review configuration baselines for web servers and management interfaces to confirm RC4 is disabled.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.