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CVE-2026-74620— net/sched: act_gact, act_police: range check the fallback control action

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基金会开源的一个操作系统内核。 Linux kernel 5.3版本存在安全漏洞，该漏洞源于net/sched的act_gact和act_police对fallback控制操作缺少范围检查，可能导致用户空间设置TC_ACT_CONSUMED值，从而造成内核内存泄漏及拒绝服务。

AI Predicted 7.5 Difficulty: Easy EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 720f22fed81bc6fd1765db7014651b6718887bea< 5f038affdacaffedf6a85a06cf59ec0a852d36a7 affected
720f22fed81bc6fd1765db7014651b6718887bea< efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4 affected
720f22fed81bc6fd1765db7014651b6718887bea< 725efc2ab4a40affc4e285a2dc4896d103948a6c affected
720f22fed81bc6fd1765db7014651b6718887bea< 6bcb8839aa2d686964a4154650afc4db91e1c514 affected
720f22fed81bc6fd1765db7014651b6718887bea< 5344e01179baa37547ab29fd7b8614f83faa190c affected
720f22fed81bc6fd1765db7014651b6718887bea< 92f00f1d4d204a428b38e26fce3baee144b6955d affected
720f22fed81bc6fd1765db7014651b6718887bea< 2e8df8c9190335475a3b64a159d3efd8cdd1cb73 affected
720f22fed81bc6fd1765db7014651b6718887bea< 883b56ae58fe657d8497806c7059646e9ba6dbd0 affected
… +10 more rows
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I. Basic Information for CVE-2026-74620

Vulnerability Information
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Vulnerability Title
net/sched: act_gact, act_police: range check the fallback control action
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: act_gact, act_police: range check the fallback control action tcf_action_check_ctrlact() range checks the primary control action: if (!opcode) ret = action > TC_ACT_VALUE_MAX ? -EINVAL : 0; TC_ACT_VALUE_MAX is TC_ACT_TRAP, so kernel-internal verdicts above it cannot be set that way. But act_gact and act_police each carry a second, independent control action supplied by user space that never reaches that helper - TCA_GACT_PROB.paction and TCA_POLICE_RESULT. Both only reject TC_ACT_GOTO_CHAIN, so any other value is stored verbatim and returned verbatim from the action. In particular user space can store TC_ACT_CONSUMED, which is TC_ACT_VALUE_MAX + 1 and is deliberately not part of the UAPI value range. That verdict tells every caller the action took ownership of the skb, so nobody frees it: sch_handle_ingress(), sch_handle_egress() and tcf_qevent_handle() all deliberately skip the free for it. The result is one leaked sk_buff plus its data buffer per packet traversing the filter, unbounded, for all traffic on the chain including kernel-generated packets. Both are trivially deterministic. act_gact clamps tcfg_pval to >= 1, so with pval = 1 gact_determ() returns the fallback for every packet. act_police has no mandatory rate, so rate = 0 leaves tcfp_mtu = ~0 and tcf_police_mtu_check() always passes. TC_ACT_CONSUMED was added by commit 720f22fed81b ("net: sched: refactor reinsert action"), after both goto-chain guards were written: commit 9469f375ab09 ("net/sched: act_gact: disallow 'goto chain' on fallback control action") and commit c08f5ed5d625 ("net/sched: act_police: disallow 'goto chain' on fallback control action"). Neither guard was widened when the new verdict appeared. Factor the existing range test out of tcf_action_check_ctrlact() as tcf_action_valid() and apply it to both fallbacks. The helper cannot call tcf_action_check_ctrlact() directly because that also allocates a goto_chain, which is exactly what these two sites must not do. Reproduced on v7.2-rc6: kmemleak reports one leaked 232-byte skbuff_head_cache object plus its 704-byte data buffer per packet. With this patch both configurations are rejected with -EINVAL and kmemleak reports none.
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基金会开源的一个操作系统内核。 Linux kernel 5.3版本存在安全漏洞，该漏洞源于net/sched的act_gact和act_police对fallback控制操作缺少范围检查，可能导致用户空间设置TC_ACT_CONSUMED值，从而造成内核内存泄漏及拒绝服务。
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 720f22fed81bc6fd1765db7014651b6718887bea ~ 5f038affdacaffedf6a85a06cf59ec0a852d36a7 -
Linux Linux 5.3 -

II. Public POCs for CVE-2026-74620

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III. Intelligence Information for CVE-2026-74620

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Patches & Fixes for CVE-2026-74620 (7)

Same Patch Batch · Linux · 2026-08-22 · 149 CVEs total

CVE-2026-74705 10.0 CRITICAL udp: fix potential use-after-free in tunnel segmentation
CVE-2026-74612 10.0 CRITICAL veth: fix skb length accounting after XDP frag adjustment
CVE-2026-74688 9.8 CRITICAL sctp: clear control chunk transport if it is being removed
CVE-2026-74669 9.8 CRITICAL ipvs: clear IPv4 options after rebasing tunnel ICMP errors
CVE-2026-74662 9.8 CRITICAL inet: frags: publish queues before arming timer
CVE-2026-74727 9.8 CRITICAL ovpn: skip rehash for peers already removed from by_id
CVE-2026-74628 9.8 CRITICAL net/x25: fix use-after-free of the socket by its timers
CVE-2026-74608 9.8 CRITICAL smb: client: Fix use-after-free in cifs_try_adding_channels()
CVE-2026-74617 9.8 CRITICAL dibs: initialise dibs->lock in dibs_dev_alloc()
CVE-2026-74597 9.8 CRITICAL ip6_tunnel: clear skb2->cb[] in ip6ip6_err()
CVE-2026-74616 9.8 CRITICAL xdp: reject clones that overrun skb_shared_info tailroom
CVE-2026-74723 9.8 CRITICAL btrfs: lzo: reject inline extents without valid headers
CVE-2026-74730 9.8 CRITICAL NFS: Pin the 'struct nfs_server' during a FREE_STATEID call
CVE-2026-74611 9.8 CRITICAL tls: rx: restore msg_iter before TLS 1.3 optimistic retry
CVE-2026-74586 9.8 CRITICAL sctp: clear new_transport when removing a peer
CVE-2026-74591 9.8 CRITICAL mm/filemap: __filemap_add_folio() restore index before retrying
CVE-2026-74587 9.8 CRITICAL sctp: fix use-after-free of cached ASCONF chunk
CVE-2026-74588 9.8 CRITICAL sctp: keep chunk->transport in step with the list it is queued on
CVE-2026-74712 9.3 CRITICAL vdpa/mlx5: Fix buffer length in create_direct_keys()
CVE-2026-74665 9.1 CRITICAL net: fix skb length accounting after generic XDP frag adjustment

Showing top 20 of 149 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-74620

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