ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF
In the Linux kernel, the following vulnerability has been resolved: ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF pppol2tp_recv() runs in the L2TP UDP-encap softirq RX path: l2tp_udp_encap_recv() -> l2tp_recv_common() -> pppol2tp_recv() -> ppp_input(&po->chan) It runs under rcu_read_lock() holding only an l2tp_session reference and takes NO reference on the internal PPP channel (struct channel, chan->ppp) that ppp_input() dereferences. The pppox socket is SOCK_RCU_FREE, so 'po' and the embedded ppp_channel are RCU-safe. But the internal struct channel is a separate allocation that ppp_release_channel() frees with a plain kfree(): close(data socket) -> pppol2tp_release() -> pppox_unbind_sock() -> ppp_unregister_channel() -> ppp_release_channel() -> kfree(pch) For a channel that is bound (PPPIOCGCHAN) but not attached to a ppp unit (no PPPIOCCONNECT, pch->ppp == NULL) and not bridged, teardown skips both ppp_disconnect_channel()'s synchronize_net() and ppp_unbridge_channels()'s synchronize_rcu(), so the kfree() has no grace period. rcu_read_lock() in pppol2tp_recv() does not protect against a plain kfree(), so an in-flight ppp_input() on one CPU can dereference the channel just freed by close() on another CPU. The bug is reachable by an unprivileged user. Defer the channel free to an RCU callback via call_rcu() so the grace period fences any in-flight ppp_input(). The disconnect and unbridge teardown paths already fence with synchronize_net()/synchronize
CVE-2026-68398
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-68398
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "4e47f1ac188ece11d6fdabe44166a2776cc5bd4e",
"versionType": "git"
},
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "110b765744b147c63882f5e9cb12931c5dc8d85f",
"versionType": "git"
},
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "4bb84e964ff0fe0a171c965362de72f9820dbce9",
"versionType": "git"
},
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "3ab32218d7182705dae5c86f13925f458072da2c",
"versionType": "git"
},
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa",
"versionType": "git"
},
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "06213c85d8c0994f786c093b8b2a517987943ca6",
"versionType": "git"
},
{
"status": "affected",
"version": "ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741",
"lessThan": "ec4215683e47424c9c4762fd3c60f552a3119142",
"versionType": "git"
},
{
"status": "affected",
"version": "d36e5ba7bbed5d7bd26e8609ffed503c2def401b",
"versionType": "git"
},
{
"status": "affected",
"version": "9bcc0508576b2d50efd958f2ea1c5906749c2c89",
"versionType": "git"
},
{
"status": "affected",
"version": "c2984681fe15cfb803a9132aaaf1140ab20a72c1",
"versionType": "git"
},
{
"status": "affected",
"version": "5803ecd7f6ac6f747582e775caa62ac9d0489261",
"versionType": "git"
},
{
"status": "affected",
"version": "26f8819ddd10141ebe7bbce700fbab36bfa5f478",
"versionType": "git"
},
{
"status": "affected",
"version": "3.2.99",
"lessThan": "3.3",
"versionType": "semver"
},
{
"status": "affected",
"version": "3.16.54",
"lessThan": "3.17",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.4.225",
"lessThan": "4.5",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.9.225",
"lessThan": "4.10",
"versionType": "semver"
},
{
"status": "affected",
"version": "4.14.182",
"lessThan": "4.15",
"versionType": "semver"
}
],
"programFiles": [
"drivers/net/ppp/ppp_generic.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.6",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/net/ppp/ppp_generic.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-68398
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #41716 · Revision 1
- Added to Heist Feed
- Publisher date