CyberSecBulletin
CVE-2026-53267NVD status: Modified

Linux: Uncontrolled Recursion

Published Updated By the CyberSecBulletin desk

CVE-2026-53267 is a high-severity uncontrolled recursion vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 15bf8091f424f97ed8bfd2385f9fca3203f27be2, af80f78ce984649e1698b841cd33f4fa505ad828, 8470f676eadeab99132708acb1a85915664d6115 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.12% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to 15bf8091f424f97ed8bfd2385f9fca3203f27be2 or af80f78ce984649e1698b841cd33f4fa505ad828 or 8470f676eadeab99132708acb1a85915664d6115 or f071b0bf078146368d18e4eec386bf2ddc0ab7e0, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.6.143 or 6.12.94 or 6.18.36 or 7.0.13, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux45d9bcda21f4c13be75e3571b0f0ef39e77934b5 up to, but not including, 15bf8091f424f97ed8bfd2385f9fca3203f27be2; 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 up to, but not including, af80f78ce984649e1698b841cd33f4fa505ad828; 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 up to, but not including, 8470f676eadeab99132708acb1a85915664d6115; 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 up to, but not including, f071b0bf078146368d18e4eec386bf2ddc0ab7e0; 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 up to, but not including, 2e154b5f53f1b0b490c7b8b02499f90feb86b1d5; 45d9bcda21f4c13be75e3571b0f0ef39e77934b5 up to, but not including, 3027ecbdb5fdf9200251c21d4818e4c447ef78e1; 4.115bf8091f424f97ed8bfd2385f9fca3203f27be2, af80f78ce984649e1698b841cd33f4fa505ad828, 8470f676eadeab99132708acb1a85915664d6115, f071b0bf078146368d18e4eec386bf2ddc0ab7e0, 2e154b5f53f1b0b490c7b8b02499f90feb86b1d5, 3027ecbdb5fdf9200251c21d4818e4c447ef78e1
LinuxLinux Kernel4.1 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.94; 6.13 up to, but not including, 6.18.36; 6.19 up to, but not including, 7.0.13; 7.16.6.143, 6.12.94, 6.18.36, 7.0.13

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

In 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

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Uncontrolled Recursion

The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.

How developers prevent this class of flaw

  • Ensure that an end condition will be reached under all logic conditions. The end condition may include checking against the depth of recursion and exiting with an error if the recursion goes too deep. The complexity of the end condition contributes to the effectiveness of this action.

More Uncontrolled Recursion vulnerabilities (CWE-674)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Uncontrolled Recursion vulnerabilities

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