netfilter: nft_ct: bail out on template ct in get eval

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-53267
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-25 09:16:44 UTC
Updated2026-07-08 04:01:59 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: netfilter: nft_ct: bail out on template ct in get eval I noticed this issue while looking at a historic syzbot report [1]. A rule like the one below is enough to trigger the bug: table ip t { chain pre { type filter hook prerouting priority raw; ct zone set 1 ct original saddr 1.2.3.4 accept } } The first expression attaches a per-cpu template ct via nft_ct_set_zone_eval() (nf_ct_tmpl_alloc -> kzalloc, tuple is all zero, nf_ct_l3num(ct) == 0). The next expression then calls nft_ct_get_eval() on the same skb, treats the template as a real ct and hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this overflows past struct nft_regs on the kernel stack; with smaller dreg values it silently clobbers adjacent registers. Reject template ct at the eval entry and in nft_ct_get_fast_eval(), mirroring the check nft_ct_set_eval() already has. Additionally, bound the address copy in NFT_CT_SRC / NFT_CT_DST by priv->len instead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple before pkt_to_tuple() fills in only the protocol-relevant leading bytes, so the trailing bytes of tuple->{src,dst}.u3.all are well-defined zero. priv->len is validated at rule load, so the copy size is now bounded by the destination register rather than by an untrusted field on the conntrack. [1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001280000 probability, percentile 0.028460000 (date 2026-07-04)

Problem Types: CWE-674

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 af80f78ce984649e1698b841cd33f4fa505ad828 git Not specified
CNA Linux Linux affected 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 8470f676eadeab99132708acb1a85915664d6115 git Not specified
CNA Linux Linux affected 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 f071b0bf078146368d18e4eec386bf2ddc0ab7e0 git Not specified
CNA Linux Linux affected 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 2e154b5f53f1b0b490c7b8b02499f90feb86b1d5 git Not specified
CNA Linux Linux affected 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 3027ecbdb5fdf9200251c21d4818e4c447ef78e1 git Not specified
CNA Linux Linux affected 4.1 Not specified
CNA Linux Linux unaffected 4.1 semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.94 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.36 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.13 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/8470f676eadeab99132708acb1a85915664d6115 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/f071b0bf078146368d18e4eec386bf2ddc0ab7e0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/2e154b5f53f1b0b490c7b8b02499f90feb86b1d5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/3027ecbdb5fdf9200251c21d4818e4c447ef78e1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/af80f78ce984649e1698b841cd33f4fa505ad828 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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