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Public proof of conceptFix available

CVE-2023-3776

A public proof of concept exists; no exploitation attested.

  • Published2023-07-21
  • Fixed in6.4.5 · 6.1.40 · 5.15.121 · 5.10.188 · 5.4.251 · 4.19.291
  • WeaknessCWE-416

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A use-after-free vulnerability in the Linux kernel's net/sched: cls_fw component can be exploited to achieve local privilege escalation. If tcf_change_indev() fails, fw_set_parms() will immediately return an error after incrementing or decrementing the reference counter in tcf_bind_filter(). If an attacker can control the reference counter and set it to zero, they can cause the reference to be freed, leading to a use-after-free vulnerability. We recommend upgrading past commit 0323bce598eea038714f941ce2b22541c46d488f.

Timeline

dates in UTC
  1. 2023-07-2121:15CVE publishedNVD
  2. 2026-10-2319:23First public proof of conceptPoC-in-GitHub

Versions per branch

NVD
Linux linux kernel
BranchAffectedFixed in
6.x≥ 6.2, < 6.4.56.4.5
6.1≥ 5.16, < 6.1.406.1.40
5.x≥ 5.11, < 5.15.1215.15.121
5.x≥ 5.5, < 5.10.1885.10.188
5.4≥ 4.20, < 5.4.2515.4.251
4.x≥ 4.15, < 4.19.2914.19.291
4.14≥ 2.6.12, < 4.14.3224.14.322
6.5= 6.5no fix published
Debian debian linux
BranchAffectedFixed in
10.0= 10.0no fix published
11.0= 11.0no fix published
12.0= 12.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As Google, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • Linux Kernelother versions: not affected

    package kernelhttps://git.kernel.org

    Affected
    • ≥ 2.6, < 6.5fixed in 6.5custom

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2024-02-02

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • bpftoolRed Hat:enterprise_linux:9::baseosall versions · fixed in 0:7.0.0-284.30.1.el9_2and 1 other package
  • bpftoolAlmaLinux:9all versions · fixed in 7.0.0-284.30.1.el9_2
  • bpftool-debuginfoRed Hat:enterprise_linux:9::crball versions · fixed in 0:7.0.0-284.30.1.el9_2
  • bpftool-debuginfoRed Hat:enterprise_linux:9::appstreamall versions · fixed in 0:7.0.0-284.30.1.el9_2
  • dtb-aarch64openSUSE:Leap 15.5all versions · fixed in 5.14.21-150500.55.19.1and 10 other packages
  • dtb-aarch64openSUSE:Leap 15.4all versions · fixed in 5.14.21-150400.24.81.1and 10 other packages
  • dtb-aarch64openSUSE:Leap 15.4all versions · fixed in 5.3.18-150300.59.130.1
  • kernelTuxCare:OracleLinux:6all versions · fixed in 2.6.32-754.35.8.el6.tuxcare.els14and 9 other packages

182 more package ranges on OSV.dev

Vendor advisories

  • RHSA-2023:7423 Red Hat Product Security155 products fixed

    Red Hat Security Advisory: kernel security update

  • RHSA-2023:7424 Red Hat Product Security30 products fixed

    Red Hat Security Advisory: kernel-rt security update

  • RHSA-2023:7398 Red Hat Product Security129 products fixed

    Red Hat Security Advisory: kernel security and bug fix update

Full record on NVD

Fix

  1. Update Linux linux kernel to 6.4.5 · 6.1.40 · 5.15.121 · 5.10.188 · 5.4.251 · 4.19.291 · 4.14.322
  2. Vendor fix Red Hat Product Security RHSA-2023:7423 · 155 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 The system must be rebooted for this update to take effect.
  3. Workaround from the vendor Red Hat Product Security RHSA-2023:7423 · 155 productsTo mitigate this issue, prevent module cls_fw from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.

Advisories and patches

Detection

read 2026-11-01 01:02 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionnone2025-03-05
  • CNACVSS 3.17.8known since 2026-10-23
  • NVDCVSS 3.17.8read 2026-10-23
  • CNAweakness (CWE)CWE-416known since 2026-10-23
  • NVDweakness (CWE)CWE-416read 2026-10-23
  • FIRST EPSSEPSS score0.5 %2026-11-08
  • PoC-in-GitHubproof of concept1known since 2026-11-01
  • OSVaffected packages—
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published
2023-07-21
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-fcg7-9x44-gx43

Frequently asked questions

What is CVE-2023-3776?

A use-after-free vulnerability in the Linux kernel's net/sched: cls_fw component can be exploited to achieve local privilege escalation. If tcf_change_indev() fails, fw_set_parms() will immediately return an error after incrementing or decrementing the reference counter in tcf_bind_filter(). If an attacker can control the reference counter and set it to zero, they can cause the reference to be freed, leading to a use-after-free vulnerability. We recommend upgrading past commit 0323bce598eea038714f941ce2b22541c46d488f.

Is CVE-2023-3776 actively exploited?

Active exploitation of CVE-2023-3776 has not been confirmed. Its EPSS score was 0.5% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2023-3776?

CVE-2023-3776 has a CVSS v3 base score of 7.8 (HIGH severity), with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

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