CVE-2026-98158— ppp_async: drop the errored frame instead of resetting its headroom
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
在 Linux 内核中，已修复以下漏洞： ppp_async：丢弃出错帧，而不是重置其 headroom（头部预留空间） 在运行 pass/active BPF 过滤器之前，会在 skb 前 prepends（前置）一个两字节的方向标签： 在接收路径上，没有任何内容能保证这两个字节的 headroom 存在。 中 的帧错误处理路径会将被重用的 skb 的 headroom 重置为零，同时声称将其恢复到全新分配的状态——但实际上，从 获取的新 skb 会携带 预留空间： 仍指向该 skb，因此下一帧将被重新组装到其中
Possible ATT&CK Techniques 1 AI
T1498 · Network Denial of ServiceAffected Version Matrix 18
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 6722e78c90054101e6797d5944cdc81af9897a0a< 25f354c55b8435d1f51b8a0a05a3cfe429358523 |
affected |
6722e78c90054101e6797d5944cdc81af9897a0a< a86a17745c3e1c6fadd4d6e90c03552dfe531c8c |
affected | ||
6722e78c90054101e6797d5944cdc81af9897a0a< ff035780adb0f49dc2c7ada26b4697849a68bec8 |
affected | ||
6722e78c90054101e6797d5944cdc81af9897a0a< c4bb894362d224b699e2f95c6c26707d9654e4a3 |
affected | ||
6722e78c90054101e6797d5944cdc81af9897a0a< d0fc3dabfe67caf084e7119ceb2ee23f5ad2f2da |
affected | ||
6722e78c90054101e6797d5944cdc81af9897a0a< 0c53eb14975f029abd6b26896a460f0d2aaefe6b |
affected | ||
6722e78c90054101e6797d5944cdc81af9897a0a< 717137221c7d90e7c98bda9a370c9da6cbf015e5 |
affected | ||
6722e78c90054101e6797d5944cdc81af9897a0a< 8dc5d98a16fa23c00999aecf10018c9f69fa5bf4 |
affected | ||
| … +10 more rows | |||
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I. Basic Information for CVE-2026-98158
Vulnerability Information
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Vulnerability Title
ppp_async: drop the errored frame instead of resetting its headroom
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved:
ppp_async: drop the errored frame instead of resetting its headroom
ppp_receive_nonmp_frame() prepends a two-byte direction tag before running
the pass/active BPF filters:
*(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_INBOUND_TAG);
Nothing on the receive path guarantees those two bytes of headroom. The
frame-error path in ppp_async's process_input_packet() resets a reused skb's
headroom to zero while claiming to restore it to a freshly allocated state -
but a fresh skb from dev_alloc_skb() carries NET_SKB_PAD:
err:
if (skb) {
/* make skb appear as freshly allocated */
skb_trim(skb, 0);
skb_reserve(skb, - skb_headroom(skb));
}
ap->rpkt still points at that skb, so the next frame is reassembled into it
with no headroom at all. A peer that sends a bad-FCS frame followed by one
beginning ff 03 then leaves a single byte of headroom by the time the filter
tag is pushed, which lands one byte below skb->head:
skbuff: skb_under_panic: len:49 put:2 head:ffff888003c10000
data:ffff888003c0ffff tail:0x30 end:0x640 dev:<NULL>
kernel BUG at net/core/skbuff.c:214!
RIP: 0010:skb_panic+0x13e/0x230
Call Trace:
skb_push+0xbd/0x100
ppp_receive_nonmp_frame+0x48a/0x1d10
ppp_input+0x4e9/0x2f80
ppp_async_process+0x2a/0xe0
tasklet_action_common+0x20f/0x8a0
handle_softirqs+0x18e/0x590
Kernel panic - not syncing: Fatal exception in interrupt
Zeroing the headroom violates the NET_SKB_PAD guarantee that dev_alloc_skb()
gives the rest of the receive path. Besides the filter panic above, when CCP
compression is enabled ppp_decompress_frame() hands skb->data - 2 to
->decompress()/->incomp(), which then reads out of bounds before skb->head
for the same reason.
Rather than restore the headroom, drop the errored frame - as ppp_synctty
already does on its error path - and clear ap->rpkt so the next frame is
reassembled into a fresh skb with proper headroom. This is simpler and fixes
both the filter under-panic and the CCP out-of-bounds read.
The original V1 of this patch made room in ppp_receive_nonmp_frame() with
skb_cow_head(); Eric pointed out that fixing the root cause in the transport
is the right approach.
Found by fuzzing the PPP receive path with a mutating peer on a pty; it is an
interesting (remote) DoS: root configures PPP, the peer supplies two crashing
frames. The reproducer (repro-ppp-skb.c, unchanged from v1) panics in about a
second, and returns cleanly with this applied.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-98158
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-98158 (8)
Same Patch Batch · Linux · 2026-09-25 · 372 CVEs total
| CVE-2026-100075 | 9.8 CRITICAL | RDMA/srpt: Fix srpt_alloc_rw_ctxs() unwind counters |
| CVE-2026-97555 | 8.8 HIGH | smb: client: fix heap overflow in DACL owner/group rewrite |
| CVE-2026-97957 | 8.8 HIGH | net: hinic: fix mailbox segment buffer overflow |
| CVE-2026-97527 | 8.8 HIGH | scsi: qla2xxx: Serialize NVMe unsol ctx list with a per-fcport lock |
| CVE-2026-97528 | 8.8 HIGH | scsi: qla2xxx: Unlink NVMe unsol ctx before freeing on LS reject error |
| CVE-2026-98115 | 8.8 HIGH | ksmbd: safely drain sessions during logoff |
| CVE-2026-97525 | 8.2 HIGH | x86/mm/pat: Allocate split page tables as kernel page tables |
| CVE-2026-98069 | 8.1 HIGH | net/rds: acquire the fastpath locks in rds_conn_shutdown() |
| CVE-2026-97573 | 8.1 HIGH | bnxt_en: Handle buffer allocation failure in bnxt_rx_ring_reset() |
| CVE-2026-97570 | 8.1 HIGH | bnxt_en: Bound SW TPA IDs to prevent crashes |
| CVE-2026-98130 | 8.1 HIGH | sctp: fix a TOCTOU race in SCTP_CMD_TIMER_START |
| CVE-2026-98070 | 8.1 HIGH | net/rds: acquire RDS_IN_XMIT in rds_tcp_reset_callbacks() |
| CVE-2026-98122 | 7.8 HIGH | vxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del() |
| CVE-2026-97575 | 7.8 HIGH | media: v4l2-ctrls: validate AV1 tile counts |
| CVE-2026-97576 | 7.8 HIGH | media: v4l2-ctrls: validate HEVC tile counts |
| CVE-2026-97941 | 7.8 HIGH | mm/slab: take n->list_lock in __slab_try_return_freelist() to avoid race |
| CVE-2026-98112 | 7.8 HIGH | ksmbd: fix listener task lifetime on netdev events |
| CVE-2026-98116 | 7.8 HIGH | ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF |
| CVE-2026-97580 | 7.8 HIGH | media: rkvdec: bound HEVC tile loops and PPS id to the array capacity |
| CVE-2026-97940 | 7.8 HIGH | ipv6: fix fib6 walker UAF on seq stop |
Showing top 20 of 372 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
Same vendor: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
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