The fanx_fingerprint function in ssl/sslxprint.c of ssldump allocates a heap buffer for formatting FAN/1 X.509 certificate fingerprints. The allocation size is computed as strlen(b64) + strlen(hex) + 31, but the format string \"fan1:x509:server:passive:%s:sha256:%s\" contains 33 fixed characters in addition to the two variable-length fields and a null terminator, requiring strlen(b64) + strlen(hex) + 34 bytes. This miscalculation results in a 3-byte heap-based buffer overflow on every invocation of the function with valid inputs. The overflow occurs because sprintf writes the full formatted string into the undersized heap buffer without bounds checking. An attacker who can supply a crafted pcap file containing a TLS X.509 certificate to a user running ssldump with FAN/1 fingerprinting enabled (for example with the -j -N options) can trigger the overflow. The resulting heap corruption may lead to denial of service through a crash or, in a worst-case scenario, arbitrary code execution in the context of the user running ssldump. The vulnerability is deterministic and requires no special privileges beyond the ability to provide input to the tool.
"}],"value":"The fanx_fingerprint function in ssl/sslxprint.c of ssldump allocates a heap buffer for formatting FAN/1 X.509 certificate fingerprints. The allocation size is computed as strlen(b64) + strlen(hex) + 31, but the format string \"fan1:x509:server:passive:%s:sha256:%s\" contains 33 fixed characters in addition to the two variable-length fields and a null terminator, requiring strlen(b64) + strlen(hex) + 34 bytes. This miscalculation results in a 3-byte heap-based buffer overflow on every invocation of the function with valid inputs. The overflow occurs because sprintf writes the full formatted string into the undersized heap buffer without bounds checking. An attacker who can supply a crafted pcap file containing a TLS X.509 certificate to a user running ssldump with FAN/1 fingerprinting enabled (for example with the -j -N options) can trigger the overflow. The resulting heap corruption may lead to denial of service through a crash or, in a worst-case scenario, arbitrary code execution in the context of the user running ssldump. The vulnerability is deterministic and requires no special privileges beyond the ability to provide input to the tool."}],"impacts":[{"capecId":"CAPEC-109","descriptions":[{"lang":"en","value":"CAPEC-109 Buffer Overflow"}]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"LOCAL","baseScore":6.8,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"ACTIVE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]},{"format":"SSVC","other":{"content":{"options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"Supplier","timestamp":"2026-10-16T05:20:29Z","version":"2.0.3"},"type":"SSVC"},"scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-122","description":"CWE-122 Heap-based Buffer Overflow","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-787","description":"CWE-787 Out-of-bounds Write","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-10-16T05:26:55.129Z","orgId":"5a6e4751-2f3f-4070-9419-94fb35b644e8","shortName":"CIRCL"},"references":[{"name":"Security patch","tags":["patch"],"url":"https://github.com/adulau/ssldump/commit/8ad55683cc0186600c085d33be5a5b627db78467"}],"solutions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"The fix replaces the hardcoded size calculation and unbounded sprintf with a two-step snprintf approach: first computing the exact required output length via snprintf(NULL, 0, format, b64, hex), then allocating precisely that length plus one byte for the null terminator via calloc, and finally writing the formatted string with a bounded snprintf. This eliminates the undersized allocation and guarantees the write never exceeds the allocated buffer.
"}],"value":"The fix replaces the hardcoded size calculation and unbounded sprintf with a two-step snprintf approach: first computing the exact required output length via snprintf(NULL, 0, format, b64, hex), then allocating precisely that length plus one byte for the null terminator via calloc, and finally writing the formatted string with a bounded snprintf. This eliminates the undersized allocation and guarantees the write never exceeds the allocated buffer."}],"source":{"discovery":"UNKNOWN"},"title":"ssldump Heap Buffer Overflow in FAN/1 X.509 Fingerprint Formatting","x_gcve":[{"extensions":{"bcp-05-x-01":{"ai_annotations":[{"ai_level":"generated","description":"Draft vulnerability metadata was generated from a git-format patch using an Ollama-hosted language model. Human validation is required before publication.","gna_source":1,"models":[{"gna_source":1,"identifier":"qwen3.8:27b","name":"qwen3.8:27b","source":"ollama"}],"review_status":"partial","scope":"record","tags":["ai-computer-assisted:llm-generated","ai-computer-assisted:classification"]}]},"bcp-05-x-02":{"x_patch2vuln":{"assumptions":["The affected version range is unspecified; the patch does not include version tags or release boundaries. All versions of ssldump containing the vulnerable fanx_fingerprint implementation prior to this commit are assumed affected.","The attack vector is assumed to be Local (AV:L) based on the common use case of analyzing pcap files. If ssldump is deployed in a live-capture configuration where an attacker can inject crafted TLS traffic, the vector could be Network (AV:N).","The 3-byte heap overflow is assumed to have the potential for code execution (VI:H, VA:H). In practice, a 3-byte overflow may more reliably cause a crash (DoS) than reliable code execution, but the worst-case impact is used for scoring.","The CAPEC-109 mapping is the closest available pattern; no CAPEC specifically addresses heap buffer overflows caused by size miscalculation.","No vendor, product version, or fixed version is specified in the patch metadata; these are marked as unknown/unspecified.","The user interaction is classified as Active (UI:A) because the user must explicitly run ssldump on a crafted input file."],"capecRationale":[{"capecId":"CAPEC-109","rationale":"CAPEC-109 describes attacks that exploit programs writing data to buffers without adequate length checking. In this case, the attacker supplies a pcap file containing a TLS X.509 certificate; ssldump processes it and the undersized heap buffer is overflowed by sprintf. The mapping is the closest available CAPEC for a heap buffer overflow triggered by crafted input. Uncertainty: CAPEC-109 is a general pattern and does not specifically call out heap overflows or off-by-N size miscalculations, but no more specific CAPEC exists in the catalog."}],"commit":"8ad55683cc0186600c085d33be5a5b627db78467","confidence":"medium","credits":[{"lang":"en","type":"remediation developer","value":"Alexandre Dulaunoy"}],"cvssRationale":"AV:L: The attacker must supply a crafted pcap file to a local instance of ssldump; no network vector is assumed. AC:L: The overflow is deterministic and triggered by any valid X.509 certificate processed through the FAN/1 fingerprint path. AT:N: No special conditions on the target are required. PR:N: No privileges beyond normal user access to run ssldump are needed. UI:A: The user must actively open or process the crafted input file. VC:N: No direct confidentiality impact is evident from a 3-byte heap overflow. VI:H: Heap corruption can lead to arbitrary code execution, compromising integrity. VA:H: Heap corruption can cause a crash, denying service. SC/SI/SA:N: No subsequent system impact is evidenced.","fixSummary":"The fix replaces the hardcoded size calculation and unbounded sprintf with a two-step snprintf approach: first computing the exact required output length via snprintf(NULL, 0, format, b64, hex), then allocating precisely that length plus one byte for the null terminator via calloc, and finally writing the formatted string with a bounded snprintf. This eliminates the undersized allocation and guarantees the write never exceeds the allocated buffer.","generatedAt":"2026-10-16T05:20:29.596478Z","generator":"patch2vuln.py","model":"qwen3.8:27b","modelComparison":{"rankings":[{"agreementScore":11,"assumptionCount":6,"confidence":"medium","model":"qwen3.8:27b","score":6}],"selectedModel":"qwen3.8:27b","selectionMethod":"deterministic-consensus-v1","selectionNotice":"The selected result is closest to model consensus; this heuristic does not establish factual correctness and human review remains required."},"patchSha256":"454d108335b2b8e3639175cd7b72e244d8bff879625ffe18e7dbbaa9ab995bfc","patchSummary":"In ssl/sslxprint.c, the fanx_fingerprint function is modified to extract the format string into a static const array, compute the exact output length using snprintf(NULL, 0, format, b64, hex), allocate fp_len + 1 bytes via calloc, and write with snprintf(fp, (size_t)fp_len + 1, format, b64, hex). A new Python regression test (tests/test_fan1_x509.py) is added that runs ssldump on a sample pcap and verifies each FAN/1 X.509 fingerprint against independently computed base64url and SHA-256 values. CMakeLists.txt is updated to register the test via CTest when Python 3 is available. The GitHub Actions CI workflow is extended to run the test suite and an additional AddressSanitizer-instrumented build to detect invalid buffer accesses.","patchTruncated":false,"patches":[{"commit":"8ad55683cc0186600c085d33be5a5b627db78467","date":"Fri, 16 Oct 2026 04:32:38 +0000","patchSha256":"454d108335b2b8e3639175cd7b72e244d8bff879625ffe18e7dbbaa9ab995bfc","source":"https://github.com/adulau/ssldump/commit/8ad55683cc0186600c085d33be5a5b627db78467.patch","sourceUrl":"https://github.com/adulau/ssldump/commit/8ad55683cc0186600c085d33be5a5b627db78467.patch","subject":"Fix heap overflow in FAN/1 X.509 fingerprint formatting"}],"source":"https://github.com/adulau/ssldump/commit/8ad55683cc0186600c085d33be5a5b627db78467.patch","ssvc":{"options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"Supplier","timestamp":"2026-10-16T05:20:29Z","version":"2.0.3"},"subject":"Fix heap overflow in FAN/1 X.509 fingerprint formatting","weaknessRationale":[{"cweId":"CWE-122","rationale":"The function allocates a heap buffer via calloc that is 3 bytes smaller than the actual formatted output, and sprintf writes past the end of the allocated region. This is a textbook heap-based buffer overflow caused by an incorrect size calculation."},{"cweId":"CWE-787","rationale":"The sprintf call writes 3 bytes beyond the end of the heap-allocated buffer, constituting an out-of-bounds write. CWE-122 is the more specific child; CWE-787 is included as the broader category."}]}},"bcp-05-x-03":{"x_timeline":{"events":[{"description":"Corrective change authored (8ad55683cc0186600c085d33be5a5b627db78467): Fix heap overflow in FAN/1 X.509 fingerprint formatting","id":"evt-fix-developed-1","references":["https://github.com/adulau/ssldump/commit/8ad55683cc0186600c085d33be5a5b627db78467.patch"],"timestamp":"2026-10-16T04:32:38Z","type":"fix-developed"}]}}},"recordType":"advisory","vulnId":"gcve-1-2026-20308"}],"x_generator":{"engine":"Vulnogram 0.2.0"}}},"cveMetadata":{"assignerOrgId":"5a6e4751-2f3f-4070-9419-94fb35b644e8","assignerShortName":"CIRCL","cveId":"CVE-2026-111458","datePublished":"2026-10-16T05:24:43.178Z","dateReserved":"2026-10-16T05:24:32.520Z","dateUpdated":"2026-10-16T05:26:55.129Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-10-16 06:17:09","lastModifiedDate":"2026-10-16 06:17:09","problem_types":["CWE-122","CWE-787","CWE-122 CWE-122 Heap-based Buffer Overflow","CWE-787 CWE-787 Out-of-bounds Write"],"metrics":{"cvssMetricV40":[{"source":"5a6e4751-2f3f-4070-9419-94fb35b644e8","type":"Secondary","cvssData":{"version":"4.0","vectorString":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","baseScore":6.8,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}],"ssvcV203":[{"source":"5a6e4751-2f3f-4070-9419-94fb35b644e8","ssvcData":{"timestamp":"2026-10-16T05:20:29Z","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"total"}],"role":"Supplier","version":"2.0.3"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"111458","Ordinal":"1","Title":"ssldump Heap Buffer Overflow in FAN/1 X.509 Fingerprint Formatti","CVE":"CVE-2026-111458","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"111458","Ordinal":"1","NoteData":"The fanx_fingerprint function in ssl/sslxprint.c of ssldump allocates a heap buffer for formatting FAN/1 X.509 certificate fingerprints. The allocation size is computed as strlen(b64) + strlen(hex) + 31, but the format string \"fan1:x509:server:passive:%s:sha256:%s\" contains 33 fixed characters in addition to the two variable-length fields and a null terminator, requiring strlen(b64) + strlen(hex) + 34 bytes. This miscalculation results in a 3-byte heap-based buffer overflow on every invocation of the function with valid inputs. The overflow occurs because sprintf writes the full formatted string into the undersized heap buffer without bounds checking. An attacker who can supply a crafted pcap file containing a TLS X.509 certificate to a user running ssldump with FAN/1 fingerprinting enabled (for example with the -j -N options) can trigger the overflow. The resulting heap corruption may lead to denial of service through a crash or, in a worst-case scenario, arbitrary code execution in the context of the user running ssldump. The vulnerability is deterministic and requires no special privileges beyond the ability to provide input to the tool.","Type":"Description","Title":"ssldump Heap Buffer Overflow in FAN/1 X.509 Fingerprint Formatti"}]}}}