{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21766","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2024-12-29T08:45:45.762Z","datePublished":"2025-02-27T02:18:16.570Z","dateUpdated":"2026-08-05T11:54:19.559Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-05T11:54:19.559Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: use RCU protection in __ip_rt_update_pmtu()\n\n__ip_rt_update_pmtu() must use RCU protection to make\nsure the net structure it reads does not disappear."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.1,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - `__ip_rt_update_pmtu()` sits directly on the ICMP Fragmentation-Needed processing path — `icmp_rcv()` → `icmp_unreach()` → protocol err handlers (`udp_err`, `raw_err`, `ping_err`, `tcp_v4_err`, `ipip_err`, GRE/vti/esp/ah err) → `ipv4_sk_update_pmtu()`/`ipv4_update_pmtu()`. A remote host anywhere on the internet reaches it with a single crafted IPv4 ICMP packet, and the attacker-supplied `un.frag.mtu` becomes the value written into the FNHE entry.\nAC:H - The attacker fully controls the read side (unlimited ICMP frag-needed floods), but the freed `struct net` only becomes reachable when a namespace teardown races a long-lived cached `dst` whose `dst->dev` still maps to the dying netns — network-namespace destruction and the exact preemption window between loading `dev->nd_net` and dereferencing it are system state a remote attacker cannot induce.\nPR:N - No authentication or credentials are involved anywhere on the path; the tunnel error handlers (`ipip_err`, GRE, vti, esp4, ah4) and `icmp_err()` dispatch on the quoted inner header alone with no socket or peer verification, so any unauthenticated host can drive `ipv4_update_pmtu()`.\nUI:N - The ICMP error is consumed entirely inside softirq packet-receive processing; no local user opens, mounts, configures, or clicks anything for the vulnerable dereference to run.\nS:U - The use-after-free read and the resulting bogus FIB lookup and FNHE writes are all confined to the kernel's own security authority; no hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - The freed `struct net` is not merely read for two sysctls — it is fed to `fib_lookup()`, which loads `net->ipv4.fib_main`/`fib_default`/`rules_ops` out of reclaimed memory and walks them as FIB tables and rule lists, so a groomed reallocation of the `net_cachep` object turns this into an attacker-directed read of arbitrary kernel addresses.\nI:H - `update_or_create_fnhe()` writes through the `fib_nh_common` returned by that poisoned lookup — `rcu_assign_pointer(nhc->nhc_exceptions, hash)`, `fnhe->fnhe_pmtu = pmtu`, `fnhe->fnhe_expires` — with `pmtu` taken verbatim from the attacker's `ntohs(icmph->un.frag.mtu)`, yielding a controlled write through a pointer chain rooted in freed memory.\nA:H - Even without weaponization, walking a FIB trie and a fib_rules list off a freed `struct net` reliably faults or corrupts state, producing a KASAN splat, oops, or panic, and the attacker can retrigger it indefinitely by replaying ICMP frag-needed packets."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/route.c"],"versions":[{"version":"2fbc6e89b2f1403189e624cabaf73e189c5e50c6","lessThan":"ce3c6165fce0f06305c806696882a3ad4b90e33f","status":"affected","versionType":"git"},{"version":"2fbc6e89b2f1403189e624cabaf73e189c5e50c6","lessThan":"ea07480b23225942208f1b754fea1e7ec486d37e","status":"affected","versionType":"git"},{"version":"2fbc6e89b2f1403189e624cabaf73e189c5e50c6","lessThan":"9b1766d1ff5fe496aabe9fc5f4e34e53f35c11c4","status":"affected","versionType":"git"},{"version":"2fbc6e89b2f1403189e624cabaf73e189c5e50c6","lessThan":"4583748b65dee4d61bd50a2214715b4237bc152a","status":"affected","versionType":"git"},{"version":"2fbc6e89b2f1403189e624cabaf73e189c5e50c6","lessThan":"a39f61d212d822b3062d7f70fa0588e50e55664e","status":"affected","versionType":"git"},{"version":"2fbc6e89b2f1403189e624cabaf73e189c5e50c6","lessThan":"139512191bd06f1b496117c76372b2ce372c9a41","status":"affected","versionType":"git"},{"version":"f415c264176e6095e9dee823e09c5bdd0ee0d337","status":"affected","versionType":"git"},{"version":"98776a365da509ad923083ae54b38ee521c52742","status":"affected","versionType":"git"},{"version":"860e2cc78c697c95bc749abb20047239fa1722ea","status":"affected","versionType":"git"},{"version":"2b1be6c925cdf4638811765a9160796291494b89","status":"affected","versionType":"git"},{"version":"4.14.200","lessThan":"4.15","status":"affected","versionType":"semver"},{"version":"4.19.148","lessThan":"4.20","status":"affected","versionType":"semver"},{"version":"5.4.68","lessThan":"5.5","status":"affected","versionType":"semver"},{"version":"5.8.12","lessThan":"5.9","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/route.c"],"versions":[{"version":"5.9","status":"affected"},{"version":"0","lessThan":"5.9","status":"unaffected","versionType":"semver"},{"version":"5.15.179","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.129","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.79","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.16","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.13.4","lessThanOrEqual":"6.13.*","status":"unaffected","versionType":"semver"},{"version":"6.14","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"5.15.179"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.1.129"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.6.79"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.12.16"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.13.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.9","versionEndExcluding":"6.14"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.14.200"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.19.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.68"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8.12"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/ce3c6165fce0f06305c806696882a3ad4b90e33f"},{"url":"https://git.kernel.org/stable/c/ea07480b23225942208f1b754fea1e7ec486d37e"},{"url":"https://git.kernel.org/stable/c/9b1766d1ff5fe496aabe9fc5f4e34e53f35c11c4"},{"url":"https://git.kernel.org/stable/c/4583748b65dee4d61bd50a2214715b4237bc152a"},{"url":"https://git.kernel.org/stable/c/a39f61d212d822b3062d7f70fa0588e50e55664e"},{"url":"https://git.kernel.org/stable/c/139512191bd06f1b496117c76372b2ce372c9a41"}],"title":"ipv4: use RCU protection in __ip_rt_update_pmtu()","x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html"}],"providerMetadata":{"orgId":"af854a3a-2127-422b-91ae-364da2661108","shortName":"CVE","dateUpdated":"2025-11-03T19:37:21.502Z"}},{"x_adpType":"supplier","providerMetadata":{"orgId":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","shortName":"siemens-SADP","dateUpdated":"2026-07-14T12:40:04.671Z"},"affected":[{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","versions":[{"status":"affected","version":"V3.1.5","lessThan":"*","versionType":"custom"}],"defaultStatus":"unknown"},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","versions":[{"status":"affected","version":"V3.1.5","lessThan":"*","versionType":"custom"}],"defaultStatus":"unknown"},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP 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