ovpn: skip rehash for peers already removed from by_id

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Summary

CVECVE-2026-74727
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-22 16:16:47 UTC
Updated2026-08-22 16:16:47 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ovpn: skip rehash for peers already removed from by_id ovpn_nl_peer_set_doit() resolves the target peer via ovpn_peer_get_by_id() before taking ovpn->lock. In the window between the lookup (which only takes a refcount) and the subsequent spin_lock_bh(&ovpn->lock), a concurrent OVPN_CMD_PEER_DEL, keepalive expiry, or socket teardown can take ovpn->lock first, run ovpn_peer_remove() to unhash the peer from all four tables (by_id, by_vpn_addr4/6, by_transp_addr) and release the lock. set_doit then acquires ovpn->lock and calls ovpn_peer_hash_vpn_ip(), which re-inserts the now-removed peer back into the rehashing tables. The same race affects the float path: ovpn_peer_endpoints_update() holds only a refcount and acquires ovpn->lock very late (after async AEAD decrypt and a netlink notification), then rehashes the peer in the by_transp_addr table. The resurrected peer becomes reachable again from the RX lookup (ovpn_peer_get_by_transp_addr) and the TX VPN-IP lookup, even though userspace believes it is gone. Once the data-path refcount drops the peer is freed via call_rcu while the hash entries embedded in it remain linked, opening a UAF window. Bail out of the rehash when hash_entry_id is unhashed, mirroring the sentinel already used by ovpn_peer_remove() to detect the already-removed state. The check is safe under ovpn->lock, which serializes every mutation of hash_entry_id, and is a no-op for the add path because ovpn_peer_add_mp() inserts hash_entry_id before calling ovpn_peer_hash_vpn_ip().

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1d36a36f6d5347360ef9681a05f6166683bafd1d d20c181088984b6eaa8d7fe7cb5ab3510988df59 git Not specified
CNA Linux Linux affected 1d36a36f6d5347360ef9681a05f6166683bafd1d 66745480298775f188b2f5ad266643e85a90f73b git Not specified
CNA Linux Linux affected 1d36a36f6d5347360ef9681a05f6166683bafd1d 33ec10567fe14456063daf549fdf1a4f53448e4c git Not specified
CNA Linux Linux affected 6.16 Not specified
CNA Linux Linux unaffected 6.16 semver Not specified
CNA Linux Linux unaffected 6.18.45 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.9 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/33ec10567fe14456063daf549fdf1a4f53448e4c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/66745480298775f188b2f5ad266643e85a90f73b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d20c181088984b6eaa8d7fe7cb5ab3510988df59 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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