pppoe: drop PFC frames

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Summary

CVECVE-2026-53003
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-24 17:17:11 UTC
Updated2026-06-24 17:17:11 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 cb3beef35ab5e0c1afca9fd7648c6ae499786377 git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 ba758fdf1399f310b30098b6faa3fd043de47dd2 git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 fcca1df05322bb04e344dd1178b54b76a08eb7c3 git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 8a5e840babc5c0fbd10c73728a13192347771ec6 git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 49e41b60ccd1bdbe9e218420f716dd5f9a2f9c71 git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 0cab5d077dd1efd2bd1a47271acc35894f945b4f git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 2b5c3c040d020e3ab3b9a8887031202d96843b1e git Not specified
CNA Linux Linux affected 7fb1b8ca8fa1ee34ffc328f17f78da68c7cc04e6 cc1ff87bce1ccd38410ab10960f576dcd17db679 git Not specified
CNA Linux Linux affected 5.0 Not specified
CNA Linux Linux unaffected 5.0 semver Not specified
CNA Linux Linux unaffected 5.10.258 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.209 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.175 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.141 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.91 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.33 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.10 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/49e41b60ccd1bdbe9e218420f716dd5f9a2f9c71 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8a5e840babc5c0fbd10c73728a13192347771ec6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cc1ff87bce1ccd38410ab10960f576dcd17db679 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fcca1df05322bb04e344dd1178b54b76a08eb7c3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cb3beef35ab5e0c1afca9fd7648c6ae499786377 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2b5c3c040d020e3ab3b9a8887031202d96843b1e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0cab5d077dd1efd2bd1a47271acc35894f945b4f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ba758fdf1399f310b30098b6faa3fd043de47dd2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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