Bug 2521382 (CVE-2026-74695)

Summary: CVE-2026-74695 kernel: netfilter: nf_flow_table: drop existing skb dst before skb_dst_set_noref()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's netfilter flow table. When processing network packets, a reference count leak can occur if a packet already has a destination entry and skb_dst_set_noref() is called. This issue can lead to a kernel warning, potentially causing system instability or a denial of service (DoS) for affected systems.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-08-22 15:42:47 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_flow_table: drop existing skb dst before skb_dst_set_noref()

Incoming skbs passing through netfilter flowtable offload hooks (or XFRM
offload path) might already carry a ref-counted dst_entry assigned during
earlier RX or routing steps.

Calling skb_dst_set_noref() when skb already holds a ref-counted dst
overwrites skb->_skb_refdst, leaking the previous dst_entry reference
count and triggering a DEBUG_NET_WARN_ON_ONCE assertion in
skb_dst_check_unset():

  WARNING: at skb_dst_check_unset include/linux/skbuff.h:1170
  WARNING: at skb_dst_set_noref include/linux/skbuff.h:1234
  WARNING: at nf_flow_offload_ip_hook+0xf6c/0x2b60 net/netfilter/nf_flow_table_ip.c:864

Drop any existing dst_entry reference with skb_dst_drop(skb) before
setting the non-referenced flowtable destination.
Comment 1 gkamathe 2026-08-24 09:55:59 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082234-CVE-2026-74695-dd6d@gregkh/T