CVE-2026-74727: Linux kernel · ovpn: skip rehash for peers already removed from by_id
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 22 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix has been implemented in the Linux kernel to address this vulnerability by adding a check to prevent rehashing of peers already removed from hash tables. Users should apply the official kernel updates that include this patch. Since this is not a cloud service, remediation depends on deploying updated kernel versions. Patch status is not explicitly stated in the provided data; users should consult their Linux distribution vendor advisories for the availability of fixed kernel versions.
Description
In 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().
References
- nvd.nist.gov/vuln/detail/CVE-2026-74727 (opens in a new tab)
- git.kernel.org/stable/c/33ec10567fe14456063daf549fdf1a4f53448e4c (opens in a new tab)
- git.kernel.org/stable/c/66745480298775f188b2f5ad266643e85a90f73b (opens in a new tab)
- git.kernel.org/stable/c/d20c181088984b6eaa8d7fe7cb5ab3510988df59 (opens in a new tab)
- ubuntu.com/security/CVE-2026-74727 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-74727 (opens in a new tab)