CVE-2024-41042 netfilter: nf_tables: prefer nft_chain_validate
A flaw in Linux kernel netfilter allows unbounded recursion during ruleset validation, causing a stack overflow and system crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-41042?
CVE-2024-41042 is a high-severity denial of service vulnerability in Linux kernel, published on 29 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_tables: prefer nft_chain_validate
nft_chain_validate already performs loop detection because a cycle will result in a call stack overflow (ctx->level >= NFT_JUMP_STACK_SIZE).
It also follows maps via ->validate callback in nft_lookup, so there appears no reason to iterate the maps again.
nf_tables_check_loops() and all its helper functions can be removed. This improves ruleset load time significantly, from 23s down to 12s.
This also fixes a crash bug. Old loop detection code can result in unbounded recursion:
BUG: TASK stack guard page was hit at .... Oops: stack guard page: 0000 [#1] PREEMPT SMP KASAN CPU: 4 PID: 1539 Comm: nft Not tainted 6.10.0-rc5+ #1 [..]
with a suitable ruleset during validation of register stores.
I can't see any actual reason to attempt to check for this from nft_validate_register_store(), at this point the transaction is still in progress, so we don't have a full picture of the rule graph.
For nf-next it might make sense to either remove it or make this depend on table->validate_state in case we could catch an error earlier (for improved error reporting to userspace).
Weakness: CWE-787
Which versions are affected by CVE-2024-41042?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-41042?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2024-41042 being exploited?
There is no known exploitation of CVE-2024-41042 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-41042, DEBIAN-CVE-2024-41042, GHSA-cc4v-r9c9-pp3h, UBUNTU-CVE-2024-41042.