CVE-2026-68398

See a problem?
Please try reporting it to the source first.
Source
https://cve.org/CVERecord?id=CVE-2026-68398
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68398.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-68398
Downstream
BELL (1)
DEBIAN (1)
MGASA (2)
openSUSE (1)
SUSE (16)
UBUNTU (1)
Related
openSUSE (1)
SUSE (16)
Published
2026-08-10T12:04:17Z
Modified
2026-10-09T18:26:43Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CVSS Calculator
Summary
ppp: defer channel free to an RCU grace period to fix pppol2tp RX UAF
Details

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_rcu(); call_rcu() does the same here without stalling the close() path.

Database specific 
{
    "cna_assigner":  "Linux",
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68398.json"
}
References

Affected packages

Git / git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git

Affected ranges

Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
ee40fb2e1eb5bc0ddd3f2f83c6e39a454ef5a741
Fixed
4e47f1ac188ece11d6fdabe44166a2776cc5bd4e
Fixed
110b765744b147c63882f5e9cb12931c5dc8d85f
Fixed
4bb84e964ff0fe0a171c965362de72f9820dbce9
Fixed
3ab32218d7182705dae5c86f13925f458072da2c
Fixed
c9574b8a8edeb4edd3ac6472c27ef7184bdb2baa
Fixed
06213c85d8c0994f786c093b8b2a517987943ca6
Fixed
ec4215683e47424c9c4762fd3c60f552a3119142
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
3.2.99
Fixed
3.3
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
3.16.54
Fixed
3.17
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4.4.225
Fixed
4.5
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4.9.225
Fixed
4.10
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
4.14.182
Fixed
4.15
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
d36e5ba7bbed5d7bd26e8609ffed503c2def401b
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
9bcc0508576b2d50efd958f2ea1c5906749c2c89
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
c2984681fe15cfb803a9132aaaf1140ab20a72c1
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
5803ecd7f6ac6f747582e775caa62ac9d0489261
Type
GIT
Repo
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Events
Introduced
26f8819ddd10141ebe7bbce700fbab36bfa5f478

Affected versions

v3.*
v3.16.54
v3.16.55
v3.16.56
v3.16.57
v3.16.58
v3.16.59
v3.16.60
v3.16.61
v3.16.62
v3.16.63
v3.16.64
v3.16.65
v3.16.66
v3.16.67
v3.16.68
v3.16.69
v3.16.70
v3.16.71
v3.16.72
v3.16.73
v3.16.74
v3.16.75
v3.16.76
v3.16.77
v3.16.78
v3.16.79
v3.16.80
v3.16.81
v3.16.82
v3.16.83
v3.16.84
v3.16.85
v3.2.100
v3.2.101
v3.2.102
v3.2.99
v4.*
v4.14.182
v4.14.183
v4.14.184
v4.14.185
v4.14.186
v4.14.187
v4.14.188
v4.14.189
v4.14.190
v4.14.191
v4.14.192
v4.14.193
v4.14.194
v4.14.195
v4.14.196
v4.14.197
v4.14.198
v4.14.199
v4.14.200
v4.14.201
v4.14.202
v4.14.203
v4.14.204
v4.14.205
v4.14.206
v4.14.207
v4.14.208
v4.14.209
v4.14.210
v4.14.211
v4.14.212
v4.14.213
v4.14.214
v4.14.215
v4.14.216
v4.14.217
v4.14.218
v4.14.219
v4.14.220
v4.14.221
v4.14.222
v4.14.223
v4.14.224
v4.14.225
v4.14.226
v4.14.227
v4.14.228
v4.14.229
v4.14.230
v4.14.231
v4.14.232
v4.14.233
v4.14.234
v4.14.235
v4.14.236
v4.14.237
v4.14.238
v4.14.239
v4.14.240
v4.14.241
v4.14.242
v4.14.243
v4.14.244
v4.14.245
v4.14.246
v4.14.247
v4.14.248
v4.14.249
v4.14.250
v4.14.251
v4.14.252
v4.14.253
v4.14.254
v4.14.255
v4.14.256
v4.14.257
v4.14.258
v4.14.259
v4.14.260
v4.14.261
v4.14.262
v4.14.263
v4.14.264
v4.14.265
v4.14.266
v4.14.267
v4.14.268
v4.14.269
v4.14.270
v4.14.271
v4.14.272
v4.14.273
v4.14.274
v4.14.275
v4.14.276
v4.14.277
v4.14.278
v4.14.279
v4.14.280
v4.14.281
v4.14.282
v4.14.283
v4.14.284
v4.14.285
v4.14.286
v4.14.287
v4.14.288
v4.14.289
v4.14.290
v4.14.291
v4.14.292
v4.14.293
v4.14.294
v4.14.295
v4.14.296
v4.14.297
v4.14.298
v4.14.299
v4.14.300
v4.14.301
v4.14.302
v4.14.303
v4.14.304
v4.14.305
v4.14.306
v4.14.307
v4.14.308
v4.14.309
v4.14.310
v4.14.311
v4.14.312
v4.14.313
v4.14.314
v4.14.315
v4.14.316
v4.14.317
v4.14.318
v4.14.319
v4.14.320
v4.14.321
v4.14.322
v4.14.323
v4.14.324
v4.14.325
v4.14.326
v4.14.327
v4.14.328
v4.14.329
v4.14.330
v4.14.331
v4.14.332
v4.14.333
v4.14.334
v4.14.335
v4.14.336
v4.4.225
v4.4.226
v4.4.227
v4.4.228
v4.4.229
v4.4.230
v4.4.231
v4.4.232
v4.4.233
v4.4.234
v4.4.235
v4.4.236
v4.4.237
v4.4.238
v4.4.239
v4.4.240
v4.4.241
v4.4.242
v4.4.243
v4.4.244
v4.4.245
v4.4.246
v4.4.247
v4.4.248
v4.4.249
v4.4.250
v4.4.251
v4.4.252
v4.4.253
v4.4.254
v4.4.255
v4.4.256
v4.4.257
v4.4.258
v4.4.259
v4.4.260
v4.4.261
v4.4.262
v4.4.263
v4.4.264
v4.4.265
v4.4.266
v4.4.267
v4.4.268
v4.4.269
v4.4.270
v4.4.271
v4.4.272
v4.4.273
v4.4.274
v4.4.275
v4.4.276
v4.4.277
v4.4.278
v4.4.279
v4.4.280
v4.4.281
v4.4.282
v4.4.283
v4.4.284
v4.4.285
v4.4.286
v4.4.287
v4.4.288
v4.4.289
v4.4.290
v4.4.291
v4.4.292
v4.4.293
v4.4.294
v4.4.295
v4.4.296
v4.4.297
v4.4.298
v4.4.299
v4.4.300
v4.4.301
v4.4.302
v4.9.225
v4.9.226
v4.9.227
v4.9.228
v4.9.229
v4.9.230
v4.9.231
v4.9.232
v4.9.233
v4.9.234
v4.9.235
v4.9.236
v4.9.237
v4.9.238
v4.9.239
v4.9.240
v4.9.241
v4.9.242
v4.9.243
v4.9.244
v4.9.245
v4.9.246
v4.9.247
v4.9.248
v4.9.249
v4.9.250
v4.9.251
v4.9.252
v4.9.253
v4.9.254
v4.9.255
v4.9.256
v4.9.257
v4.9.258
v4.9.259
v4.9.260
v4.9.261
v4.9.262
v4.9.263
v4.9.264
v4.9.265
v4.9.266
v4.9.267
v4.9.268
v4.9.269
v4.9.270
v4.9.271
v4.9.272
v4.9.273
v4.9.274
v4.9.275
v4.9.276
v4.9.277
v4.9.278
v4.9.279
v4.9.280
v4.9.281
v4.9.282
v4.9.283
v4.9.284
v4.9.285
v4.9.286
v4.9.287
v4.9.288
v4.9.289
v4.9.290
v4.9.291
v4.9.292
v4.9.293
v4.9.294
v4.9.295
v4.9.296
v4.9.297
v4.9.298
v4.9.299
v4.9.300
v4.9.301
v4.9.302
v4.9.303
v4.9.304
v4.9.305
v4.9.306
v4.9.307
v4.9.308
v4.9.309
v4.9.310
v4.9.311
v4.9.312
v4.9.313
v4.9.314
v4.9.315
v4.9.316
v4.9.317
v4.9.318
v4.9.319
v4.9.320
v4.9.321
v4.9.322
v4.9.323
v4.9.324
v4.9.325
v4.9.326
v4.9.327
v4.9.328
v4.9.329
v4.9.330
v4.9.331
v4.9.332
v4.9.333
v4.9.334
v4.9.335
v4.9.336
v4.9.337

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68398.json"

Linux / Kernel

Package

Name
Kernel

Affected ranges

Type
ECOSYSTEM
Events
Introduced
4.15.0
Fixed
5.15.216
Type
ECOSYSTEM
Events
Introduced
5.16.0
Fixed
6.1.183
Type
ECOSYSTEM
Events
Introduced
6.2.0
Fixed
6.6.148
Type
ECOSYSTEM
Events
Introduced
6.7.0
Fixed
6.12.101
Type
ECOSYSTEM
Events
Introduced
6.13.0
Fixed
6.18.42
Type
ECOSYSTEM
Events
Introduced
6.19.0
Fixed
7.1.6

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68398.json"