CyberSecBulletin
CVE-2026-31657NVD status: Modified

Linux: NULL Pointer Dereference

Published Updated By the CyberSecBulletin desk

CVE-2026-31657 is a critical-severity NULL pointer dereference vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 5202f071b367ffbc8e279fc7a00db14f5e587f52, 69d1ce9c72eca91203ffdb8d08bacd511100aec6, f4858832ddef2f39f21e30b7226bbcd3c4b2bc96 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 0.4% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to 5202f071b367ffbc8e279fc7a00db14f5e587f52 or 69d1ce9c72eca91203ffdb8d08bacd511100aec6 or f4858832ddef2f39f21e30b7226bbcd3c4b2bc96 or 2f55b58b5a0bbed192d60c444a45a49cdf1b545f, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.169 or 6.6.135 or 6.12.82 or 6.18.23, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 5202f071b367ffbc8e279fc7a00db14f5e587f52; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 69d1ce9c72eca91203ffdb8d08bacd511100aec6; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, f4858832ddef2f39f21e30b7226bbcd3c4b2bc96; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 2f55b58b5a0bbed192d60c444a45a49cdf1b545f; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 7962b522222628596ca9ecc8722efc95367aadbd; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 4dee4c0688443aaf5bbec74aa203c851d1d53c35; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 1f2dc36c297d27733f1b380ea644cf15a361bd7b; 23721387c409087fd3b97e274f34d3ddc0970b74 up to, but not including, 82d8701b2c930d0e96b0dbc9115a218d791cb0d2; and 1 more ranges5202f071b367ffbc8e279fc7a00db14f5e587f52, 69d1ce9c72eca91203ffdb8d08bacd511100aec6, f4858832ddef2f39f21e30b7226bbcd3c4b2bc96, 2f55b58b5a0bbed192d60c444a45a49cdf1b545f, 7962b522222628596ca9ecc8722efc95367aadbd, 4dee4c0688443aaf5bbec74aa203c851d1d53c35
LinuxLinux Kernel3.5.1 up to, but not including, 6.1.169; 6.2 up to, but not including, 6.6.135; 6.7 up to, but not including, 6.12.82; 6.13 up to, but not including, 6.18.23; 6.19 up to, but not including, 6.19.13; 3.5; 7.06.1.169, 6.6.135, 6.12.82, 6.18.23, 6.19.13

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
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
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:N/AC:L/PR:N/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: batman-adv: hold claim backbone gateways by reference batadv_bla_add_claim() can replace claim->backbone_gw and drop the old gateway's last reference while readers still follow the pointer. The netlink claim dump path dereferences claim->backbone_gw->orig and takes claim->backbone_gw->crc_lock without pinning the underlying backbone gateway. batadv_bla_check_claim() still has the same naked pointer access pattern. Reuse batadv_bla_claim_get_backbone_gw() in both readers so they operate on a stable gateway reference until the read-side work is complete. This keeps the dump and claim-check paths aligned with the lifetime rules introduced for the other BLA claim readers.

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

The underlying weakness: NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL.

How developers prevent this class of flaw

  • For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
  • Select a programming language that is not susceptible to these issues.
  • Check the results of all functions that return a value and verify that the value is non-null before acting upon it.

More NULL Pointer Dereference vulnerabilities (CWE-476)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent NULL Pointer Dereference vulnerabilities

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