Linux KernelOperating system · Linux

CVE-2024-49946

MEDIUM · 5.5 CVSS v3.1 Published 2024-10-21

Fix available

A fix is available. Upgrade to 5.15.168 / 6.1.113 or later.

See remediation →

57/100

Remediation priority · Elevated

Zero-click Patch available

Official description

NVD · unedited

In the Linux kernel, the following vulnerability has been resolved: ppp: do not assume bh is held in ppp_channel_bridge_input() Networking receive path is usually handled from BH handler. However, some protocols need to acquire the socket lock, and packets might be stored in the socket backlog is the socket was owned by a user process. In this case, release_sock(), __release_sock(), and sk_backlog_rcv() might call the sk->sk_backlog_rcv() handler in process context. sybot caught ppp was not considering this case in ppp_channel_bridge_input() : WARNING: inconsistent lock state 6.11.0-rc7-syzkaller-g5f5673607153 #0 Not tainted -------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. ksoftirqd/1/24 [HC0[0]:SC1[1]:HE1:SE0] takes: ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline] ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304 {SOFTIRQ-ON-W} state was registered at: lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x48/0x60 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline] ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304 pppoe_rcv_core+0xfc/0x314 drivers/net/ppp/pppoe.c:379 sk_backlog_rcv include/net/sock.h:1111 [inline] __release_sock+0x1a8/0x3d8 net/core/sock.c:3004 release_sock+0x68/0x1b8 net/core/sock.c:3558 pppoe_sendmsg+0xc8/0x5d8 drivers/net/ppp/pppoe.c:903 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] __sys_sendto+0x374/0x4f4 net/socket.c:2204 __do_sys_sendto net/socket.c:2216 [inline] __se_sys_sendto net/socket.c:2212 [inline] __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2212 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598 irq event stamp: 282914 hardirqs last enabled at (282914): [<ffff80008b42e30c>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] hardirqs last enabled at (282914): [<ffff80008b42e30c>] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:194 hardirqs last disabled at (282913): [<ffff80008b42e13c>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline] hardirqs last disabled at (282913): [<ffff80008b42e13c>] _raw_spin_lock_irqsave+0x2c/0x7c kernel/locking/spinlock.c:162 softirqs last enabled at (282904): [<ffff8000801f8e88>] softirq_handle_end kernel/softirq.c:400 [inline] softirqs last enabled at (282904): [<ffff8000801f8e88>] handle_softirqs+0xa3c/0xbfc kernel/softirq.c:582 softirqs last disabled at (282909): [<ffff8000801fbdf8>] run_ksoftirqd+0x70/0x158 kernel/softirq.c:928 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&pch->downl); <Interrupt> lock(&pch->downl); *** DEADLOCK *** 1 lock held by ksoftirqd/1/24: #0: ffff80008f74dfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:325 stack backtrace: CPU: 1 UID: 0 PID: 24 Comm: ksoftirqd/1 Not tainted 6.11.0-rc7-syzkaller-g5f5673607153 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Call trace: dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:319 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:326 __dump_sta ---truncated---

Technical summary

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions

NVD · CPE data

Linux KernelOperating system

Affected:>= 5.11, < 5.15.168>= 5.16, < 6.1.113>= 6.2, < 6.6.55>= 6.7, < 6.10.14>= 6.11, < 6.11.3= 6.12

CVSS breakdown

From the vector

Attack vector: Local
Complexity: Low
Privileges: Low
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation

dbcve · scoped

Upgrade available Upgrade to 5.15.168 / 6.1.113 / 6.6.55 or later

Fixed in 5.15.1686.1.1136.6.55

Vendor patch git.kernel.org →

Recommended fix High confidence

Upgrade to Linux kernel 5.15.168, 6.1.113, 6.6.55, or 6.10.14 (or later stable release) depending on your current branch

Identify the currently running Linux kernel version using `uname -r`
Determine which kernel branch you're running (e.g., 5.15.x, 6.1.x, 6.2.x, 6.7.x)
Upgrade to the fixed version for your branch: for 5.11-5.15.x upgrade to 5.15.168 or later; for 5.16-6.1.x upgrade to 6.1.113 or later; for 6.2-6.6.x upgrade to 6.6.55 or later; for 6.7-6.10.x upgrade to 6.10.14 or later
After kernel upgrade, reboot the system to load the fixed kernel
Verify the fix is applied by checking the kernel version and confirming the patch commit 176dd41e8c2bd997ed3d66568a3362e69ecce99b is included

Caveat Kernel upgrades may require rebuild of out-of-tree modules; ensure compatible drivers/modules are available before rebooting

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-49946 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2024-49946?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

A fix existsUpgrade to 5.15.168 / 6.1.113 or later

Severity 5.5 Medium

Exploit likelihood EPSS, next 30 days 0.2%

Affects: Linux Kernel

Remediation

Need this fixed?

Get a fix

Estimated effortfrom ~9 hrs

ComplexityModerate

Typical engagementfrom $1,600

What a fix involves

We scope it with you and confirm a fixed quote
A specialist builds a reviewed fix
You deploy it to staging first
Optional re-test once it’s live

We specialise in CVE remediation. Send your environment and we’ll scope CVE-2024-49946 and return a fixed quote.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Remediation

References