Re: [cip-dev] New CVE entries in this week

Pavel Machek
2021-12-09T09:21:05Z

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Hi!

> * New CVEs
>
> CVE-2021-39636: "no details"
>
> CVSS v3 score is not provided
>
> There is no vulnerability details yet. However, there is five patches
> are addressed so the bug is in the netfilter module.
>
> f32815d ("xtables: add xt_match, xt_target and data copy_to_user
> functions"): merged in 4.11-rc1
> f77bc5b ("iptables: use match, target and data copy_to_user helpers"):
> merged in 4.11-rc1
> e47ddb2 ("ip6tables: use match, target and data copy_to_user
> helpers"): merged in 4.11-rc1
> ec23189 ("xtables: extend matches and targets with .usersize"): merged
> in 4.11-rc1
> 1e98ffe ("netfilter: x_tables: fix pointer leaks to userspace"):
> merged in 4.16-rc1. This fixes commit ec23189 ("xtables: extend
> matches and targets with .usersize") that was merged in 4.11-rc1.
>
> Fixed status
>
> mainline: [f32815d21d4d8287336fb9cef4d2d9e0866214c2,
> f77bc5b23fb1af51fc0faa8a479dea8969eb5079,
> e47ddb2c4691fd2bd8d25745ecb6848408899757,
> ec23189049651b16dc2ffab35a4371dc1f491aca,
> 1e98ffea5a8935ec040ab72299e349cb44b8defd]
> stable/4.14: [f32815d21d4d8287336fb9cef4d2d9e0866214c2,
> f77bc5b23fb1af51fc0faa8a479dea8969eb5079,
> e47ddb2c4691fd2bd8d25745ecb6848408899757,
> ec23189049651b16dc2ffab35a4371dc1f491aca,
> ad10785a706e63ff155fc97860cdcc5e3bc5992d]

Hmm. Fun. 1e98ffea5a8935ec040ab72299e349cb44b8defd may have a clue:

This leads to kernel pointer leaks if a match/target is set
and then read back to userspace.

So that sounds like KASLR workaround? iptables are normally limited to
priviledged users, and KASLR is just a technology to make exploitation
hard. I don't think we care too much here.

> CVE-2018-25020: bpf: fix truncated jump targets on heavy expansions
>
> CVSS v3 score is not provided
>
> Fixed status
>
> The BPF subsystem in the kernel through 4.17-rc7 has overflow bug.
>
> mainline: [050fad7c4534c13c8eb1d9c2ba66012e014773cb]

Fun. JITs are hard to get right. I guess "avoid BPF" and "certainly
don't allow unpriviledged access to BPF" is good advice.

Best regards,
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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