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CVE-2021-47546— ipv6: fix memory leak in fib6_rule_suppress

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.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于存在内存泄漏。

AI Predicted 5.3 Difficulty: Easy EPSS 0.22% · P12

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux ca7a03c4175366a92cee0ccc4fec0038c3266e26< ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29 affected
ca7a03c4175366a92cee0ccc4fec0038c3266e26< 209d35ee34e25f9668c404350a1c86d914c54ffa affected
ca7a03c4175366a92cee0ccc4fec0038c3266e26< 8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383 affected
ca7a03c4175366a92cee0ccc4fec0038c3266e26< cdef485217d30382f3bf6448c54b4401648fe3f1 affected
d37c966752043733eb847dd897d6e3405084c559 affected
ecc265624956ea784cb2bd2b31a95bd54c4f5f13 affected
5.2.19< 5.3 affected
5.3.4< 5.4 affected
… +6 more rows
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I. Basic Information for CVE-2021-47546

Vulnerability Information
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Vulnerability Title
ipv6: fix memory leak in fib6_rule_suppress
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: fix memory leak in fib6_rule_suppress The kernel leaks memory when a `fib` rule is present in IPv6 nftables firewall rules and a suppress_prefix rule is present in the IPv6 routing rules (used by certain tools such as wg-quick). In such scenarios, every incoming packet will leak an allocation in `ip6_dst_cache` slab cache. After some hours of `bpftrace`-ing and source code reading, I tracked down the issue to ca7a03c41753 ("ipv6: do not free rt if FIB_LOOKUP_NOREF is set on suppress rule"). The problem with that change is that the generic `args->flags` always have `FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag `RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not decreasing the refcount when needed. How to reproduce: - Add the following nftables rule to a prerouting chain: meta nfproto ipv6 fib saddr . mark . iif oif missing drop This can be done with: sudo nft create table inet test sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }' sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop - Run: sudo ip -6 rule add table main suppress_prefixlength 0 - Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase with every incoming ipv6 packet. This patch exposes the protocol-specific flags to the protocol specific `suppress` function, and check the protocol-specific `flags` argument for RT6_LOOKUP_F_DST_NOREF instead of the generic FIB_LOOKUP_NOREF when decreasing the refcount, like this. [1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71 [2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99
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
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于存在内存泄漏。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux ca7a03c4175366a92cee0ccc4fec0038c3266e26 ~ ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29 -
Linux Linux 5.4 -

II. Public POCs for CVE-2021-47546

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III. Intelligence Information for CVE-2021-47546

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Other References for CVE-2021-47546 (4)

Same Patch Batch · Linux · 2024-05-24 · 72 CVEs total

CVE-2021-47544 9.8 CRITICAL tcp: fix page frag corruption on page fault
CVE-2021-47506 9.8 CRITICAL nfsd: fix use-after-free due to delegation race
CVE-2021-47536 9.8 CRITICAL net/smc: fix wrong list_del in smc_lgr_cleanup_early
CVE-2021-47520 8.8 HIGH can: pch_can: pch_can_rx_normal: fix use after free
CVE-2023-52880 7.8 HIGH tty: n_gsm: require CAP_NET_ADMIN to attach N_GSM0710 ldisc
CVE-2021-47505 7.8 HIGH aio: fix use-after-free due to missing POLLFREE handling
CVE-2021-47512 7.8 HIGH net/sched: fq_pie: prevent dismantle issue
CVE-2021-47502 7.8 HIGH ASoC: codecs: wcd934x: handle channel mappping list correctly
CVE-2021-47517 7.8 HIGH ethtool: do not perform operations on net devices being unregistered
CVE-2021-47533 7.8 HIGH drm/vc4: kms: Clear the HVS FIFO commit pointer once done
CVE-2021-47500 7.8 HIGH iio: mma8452: Fix trigger reference couting
CVE-2021-47541 7.8 HIGH net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources()
CVE-2021-47552 7.8 HIGH blk-mq: cancel blk-mq dispatch work in both blk_cleanup_queue and disk_release()
CVE-2021-47551 7.8 HIGH drm/amd/amdkfd: Fix kernel panic when reset failed and been triggered again
CVE-2021-47555 7.8 HIGH net: vlan: fix underflow for the real_dev refcnt
CVE-2021-47561 7.8 HIGH i2c: virtio: disable timeout handling
CVE-2021-47535 7.8 HIGH drm/msm/a6xx: Allocate enough space for GMU registers
CVE-2021-47559 7.5 HIGH net/smc: Fix NULL pointer dereferencing in smc_vlan_by_tcpsk()
CVE-2021-47515 7.5 HIGH seg6: fix the iif in the IPv6 socket control block
CVE-2021-47554 vdpa_sim: avoid putting an uninitialized iova_domain

Showing top 20 of 72 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2021-47546

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