GHSA-VXQR-379F-FHC4
Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-22 18:30In 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().
{
"affected": [],
"aliases": [
"CVE-2026-74727"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-22T16:16:47Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\novpn: skip rehash for peers already removed from by_id\n\novpn_nl_peer_set_doit() resolves the target peer via\novpn_peer_get_by_id() before taking ovpn-\u003elock. In the window between\nthe lookup (which only takes a refcount) and the subsequent\nspin_lock_bh(\u0026ovpn-\u003elock), a concurrent OVPN_CMD_PEER_DEL, keepalive\nexpiry, or socket teardown can take ovpn-\u003elock first, run\novpn_peer_remove() to unhash the peer from all four tables (by_id,\nby_vpn_addr4/6, by_transp_addr) and release the lock. set_doit then\nacquires ovpn-\u003elock and calls ovpn_peer_hash_vpn_ip(), which\nre-inserts the now-removed peer back into the rehashing tables.\n\nThe same race affects the float path: ovpn_peer_endpoints_update()\nholds only a refcount and acquires ovpn-\u003elock very late (after async\nAEAD decrypt and a netlink notification), then rehashes the peer\nin the by_transp_addr table.\n\nThe resurrected peer becomes reachable again from the RX lookup\n(ovpn_peer_get_by_transp_addr) and the TX VPN-IP lookup, even though\nuserspace believes it is gone. Once the data-path refcount drops the\npeer is freed via call_rcu while the hash entries embedded in it\nremain linked, opening a UAF window.\n\nBail out of the rehash when hash_entry_id is unhashed, mirroring\nthe sentinel already used by ovpn_peer_remove() to detect the\nalready-removed state. The check is safe under ovpn-\u003elock, which\nserializes every mutation of hash_entry_id, and is a no-op for the\nadd path because ovpn_peer_add_mp() inserts hash_entry_id before\ncalling ovpn_peer_hash_vpn_ip().",
"id": "GHSA-vxqr-379f-fhc4",
"modified": "2026-08-22T18:30:30Z",
"published": "2026-08-22T18:30:30Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74727"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/33ec10567fe14456063daf549fdf1a4f53448e4c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/66745480298775f188b2f5ad266643e85a90f73b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d20c181088984b6eaa8d7fe7cb5ab3510988df59"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.