{"id":"CVE-2026-23139","state":"PUBLISHED","title":"netfilter: nf_conncount: update last_gc only when GC has been performed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conncount: update last_gc only when GC has been performed\n\nCurrently last_gc is being updated everytime a new connection is\ntracked, that means that it is updated even if a GC wasn't performed.\nWith a sufficiently high packet rate, it is possible to always bypass\nthe GC, causing the list to grow infinitely.\n\nUpdate the last_gc value only when a GC has been actually performed.","publishedAt":"2026-02-14T15:22:24.059Z","updatedAt":"2026-08-05T12:20:21.709Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f106694733c66a48740c25bc4e212e9b2ea364ce","status":"affected","lessThan":"2c7c71113ed6d3e2f3aca4c088f22283016ff34f","versionType":"git"},{"version":"be69850b461e7b491d87a22e33ab76fdd04b725e","status":"affected","lessThan":"c4cde57c8affdcca5bcff53a1047e15d268bdca1","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"9f45588993d7f115280fc726119ca86fba32a811","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"3cd717359e56f82f06cbf8279b47a7d79880c6f3","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"26a82dce2beee39c43c109d9647e16f49cb02a35","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"8bdafdf4900040a81422056cabe5e00a37bd101a","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"7811ba452402d58628e68faedf38745b3d485e3c","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conncount.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.1.161","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.121","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.66","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.6","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conncount.c"]}],"references":["https://git.kernel.org/stable/c/2c7c71113ed6d3e2f3aca4c088f22283016ff34f","https://git.kernel.org/stable/c/c4cde57c8affdcca5bcff53a1047e15d268bdca1","https://git.kernel.org/stable/c/9f45588993d7f115280fc726119ca86fba32a811","https://git.kernel.org/stable/c/3cd717359e56f82f06cbf8279b47a7d79880c6f3","https://git.kernel.org/stable/c/26a82dce2beee39c43c109d9647e16f49cb02a35","https://git.kernel.org/stable/c/8bdafdf4900040a81422056cabe5e00a37bd101a","https://git.kernel.org/stable/c/7811ba452402d58628e68faedf38745b3d485e3c"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23139.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23139","state":"PUBLISHED","datePublished":"2026-02-14T15:22:24.059Z","dateUpdated":"2026-08-05T12:20:21.709Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:45.972Z"},"containers":{"cna":{"title":"netfilter: nf_conncount: update last_gc only when GC has been performed","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conncount: update last_gc only when GC has been performed\n\nCurrently last_gc is being updated everytime a new connection is\ntracked, that means that it is updated even if a GC wasn't performed.\nWith a sufficiently high packet rate, it is possible to always bypass\nthe GC, causing the list to grow infinitely.\n\nUpdate the last_gc value only when a GC has been actually performed."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f106694733c66a48740c25bc4e212e9b2ea364ce","status":"affected","lessThan":"2c7c71113ed6d3e2f3aca4c088f22283016ff34f","versionType":"git"},{"version":"be69850b461e7b491d87a22e33ab76fdd04b725e","status":"affected","lessThan":"c4cde57c8affdcca5bcff53a1047e15d268bdca1","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"9f45588993d7f115280fc726119ca86fba32a811","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"3cd717359e56f82f06cbf8279b47a7d79880c6f3","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"26a82dce2beee39c43c109d9647e16f49cb02a35","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"8bdafdf4900040a81422056cabe5e00a37bd101a","versionType":"git"},{"version":"d265929930e2ffafc744c0ae05fb70acd53be1ee","status":"affected","lessThan":"7811ba452402d58628e68faedf38745b3d485e3c","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conncount.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.1.161","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.121","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.66","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.6","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conncount.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2c7c71113ed6d3e2f3aca4c088f22283016ff34f"},{"url":"https://git.kernel.org/stable/c/c4cde57c8affdcca5bcff53a1047e15d268bdca1"},{"url":"https://git.kernel.org/stable/c/9f45588993d7f115280fc726119ca86fba32a811"},{"url":"https://git.kernel.org/stable/c/3cd717359e56f82f06cbf8279b47a7d79880c6f3"},{"url":"https://git.kernel.org/stable/c/26a82dce2beee39c43c109d9647e16f49cb02a35"},{"url":"https://git.kernel.org/stable/c/8bdafdf4900040a81422056cabe5e00a37bd101a"},{"url":"https://git.kernel.org/stable/c/7811ba452402d58628e68faedf38745b3d485e3c"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerability is triggered by network packets hitting connlimit rules (xt_connlimit, nft_connlimit) or OVS zone limits. A remote unauthenticated attacker can send a flood of packets to trigger the unbounded list growth.\nAC:L - The attacker fully controls the packet rate needed to bypass GC. The nf_conncount module is only loaded when connlimit is in use, so its deployment inherently implies connlimit rules exist. Exploitation is completely reliable.\nPR:N - No authentication or privileges are needed to send network packets that match connlimit rules. The attack is in the packet processing path, not the rule configuration path.\nUI:N - No user interaction is required. The attacker autonomously sends packets to trigger the vulnerability.\nS:U - The impact (kernel memory exhaustion) stays within the kernel's security boundary. No cross-boundary impact such as VM escape.\nC:N - This is a resource exhaustion bug where stale connections are never garbage collected. No information is disclosed to the attacker.\nI:N - No data modification or memory corruption occurs. The list simply grows unboundedly but the entries themselves are well-formed.\nA:H - The connection list grows infinitely, exhausting kernel slab memory via unbounded GFP_ATOMIC allocations. This leads to OOM conditions, system instability, and potential kernel panic."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:20:21.709Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.1.161"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.6.121"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.12.66"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.18.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.19"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}