CVE Catalog

CVE-2026-53003

HighCVSS 7.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.51%

40th percentile - higher than 40% of all known CVEs

Summary

A vulnerability in the Linux kernel's PPPoE driver allows dropping frames with Protocol Field Compression (PFC). An attacker can send a crafted frame with a 1-byte protocol field, shifting the payload by one byte and potentially causing unaligned access exceptions on some architectures.

Risk Assessment

The risk involves a potential denial-of-service (DoS) attack by triggering memory access exceptions, which could destabilize the system or cause a crash.

Recommendation

It is recommended to immediately update the Linux kernel to a version containing the fix that drops PFC frames in PPPoE to reduce the attack surface.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

In the Linux kernel, the following vulnerability has been resolved: pppoe: drop PFC frames RFC 2516 Section 7 states that Protocol Field Compression (PFC) is NOT RECOMMENDED for PPPoE. In practice, pppd does not support negotiating PFC for PPPoE sessions, and the current PPPoE driver assumes an uncompressed (2-byte) protocol field. However, the generic PPP layer function ppp_input() is not aware of the negotiation result, and still accepts PFC frames. If a peer with a broken implementation or an attacker sends a frame with a compressed (1-byte) protocol field, the subsequent PPP payload is shifted by one byte. This causes the network header to be 4-byte misaligned, which may trigger unaligned access exceptions on some architectures. To reduce the attack surface, drop PPPoE PFC frames. Introduce ppp_skb_is_compressed_proto() helper function to be used in both ppp_generic.c and pppoe.c to avoid open-coding.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS